D is for Double Down



D. See double down.

D2. Acronym for “double down on any first 2 cards.”  See DA. See DOA.

D3. Acronym for “double down on 3 or more cards.”

D4. Acronym for “double down on first four or fewer cards.”

D8. Acronym for “double down on 8, 9, 10, 11 only.”

D9. Acronym for “double down on 9, 10, 11 only.”

D10. Acronym for “double down on 10 and 11 only.”

D11. Acronym for “double down on 11 only.”

DA. Acronym for “double down on any first two cards.”   See D2. See DOA.

DA2. Acronym for “double down on any first two cards.”  See DA.  See D2. See DOA.

DAB. See Double Attack Blackjack.

DACE. Acronym for “double down but not hit after splitting aces”.  See DSA.

Dakota.  In 2016, South Dakota had 19 casinos with 67 blackjack tables.  North Dakota had 2 casinos with 10 blackjack tables.
[ qfit.com/maps.shtml ]
[ 82 Ristvedt The North Dakota Blackjack Book ]

Dakota Rules  Archived Rules

D’Alembert. {PBS} (Jean le Rond D’Alembert) Also called the chop, pyramid, up-and-down or the seesaw system. A progressive betting system where the goal is to win one unit. On losses betting progresses as follows: 1 2 3 4 5 6 7 8 9… On wins betting is lowered by one unit until your bankroll returns to zero. The Contra-D’Alembert is just the opposite where the player increases bets after each win and reduces it by one after each loss.  This system is NOT recommended… unless you are using it for cover.
[ 79 Ainslie How to Gamble in a Casino 69 ] [ 77 C&S Vol2, 5 ]

Dalton Teaching in his Younger YearsDalton, MichaelAuthor of the book The Encyclopedia of Blackjack (this book) and editor of the Blackjack Review Network.   Former publisher of Blackjack Review magazine (1992-1998).  Dalton has a Bachelor of Science degree in Space Science / Physics and a Master of Science in Space Technology and is retired from the National Aeronautics and Space Administration (NASA) where he worked for over 30 years. His other interests (besides blackjack and poker) include the martial arts where he has a black belt in Tae Kwon Do and playing the Scottish bagpipes.  See About the Author.  You can contact him directly using this contact form.
[ Photo: Michael Dalton Teaching Blackjack in his Younger Years (c1992) ]
[ BJRnet.com ] [ BlackjackReview.com ] [ BJRNET: Articles ] [ WIKIPEDIA ] [ TWITTER ] [ FACEBOOK ] [ PODCAST: 04/16/20 ]

Blackjack FAQFrequently Asked Question
If blackjack is really “beatable” then why aren’t you out there making millions of dollars instead of writing about it?

DAH. An NBJ acronym for dealer average hand.

DAS. Acronym for double after split.

database. See history.

David. (c1971) A concealable blackjack computer developed by Keith Taft. Taft designed his first such strategy computer and used it successfully in Nevada’s casinos in 1971. Arnold Snyder reportedly wrote the manual for this computer. This device is a perfect-strategy computer. George and Thor were reportedly later versions of David. See Casey. See Fred.
[ 4/16/79 Sports Illustrated ] [ 1/80 Gambling Times ] [ 6/84 Snyder BJF 4 ] [ 9/84 Snyder Snyder Writes Manual for David BJF ]

Davis, E. CliftonDeveloper of the New Blackjack (NBJ) method. This system or “method” is NOT recommended.
[ ARCHIVE:  ECliftonDavis.com 1999 ]

daub. {CHS}. As in a card-dauber. A paste or fluid (e.g., India ink or aniline pencil) used to mark the back of playing cards for the purposes of cheating. Also called rouge or smear.

DBH Count. {PCS/L?} (David Barrios) (c1986) ???

DBR. An NBJ acronym for dealer break rate.

DBS. An acronym for double after split but not typically used in this book.
[ Wong CBN ]

DBX. Acronym for Double Exposure.  See DE.

DC17. Acronym for dealer’s choice on whether to hit or stand on S-17.

DCS. Acronym for Digital Card System. See Digital 21.

DD. 1) Acronym for Double Down. 2) Acronym for Double-Deck. 3) Acronym for Double Diamond Blackjack.

DDD.  Acronym for Double again after doubling and getting a card.

DDRAcronym for Double Down Rescue.

DE. Acronym for Double Exposure.  See DE.  See DBX.

Dead Man’s Hand.  A blackjack side bet by Dunow Gaming which pays if one of the player’s first two cards is an eight or an ace.  Seen in South Dakota.  HA = 4.45% – 4.98%
[ wizardofodds.com ]

dead table. A casino term referring to a table with no players.

deal. 1) As in to deal cards. The act of distributing cards to a player or players. Dealers will always deal from left to right. 2) As in the deal. The same as hand. See payoff.

dealer. The casino employee conducting the blackjack game, dealing the cards, making the payoffs and seeing that rules are followed at his or her table. All casino dealers are instructed to play their hands according to a fixed and specified set of instructions. For example, all dealers must hit a 16 and stand on hard 17, even if all players have hands of 18 or more. According to one instructor the three basic elements to a good “21” dealer are the following:

  • Protection of the game.
  • Uniformity and readability.
  • Speed and Accuracy.

See S-17. See H-17.  See no-peek devices.  See dealer odds.
[ 11/81 Wong Casino Rules… – NVB Vol.3,182 ] [ 82 Gaem Keeping Notes on BJ Dealers Vol.20,26 ] [ 85 Do Dealers Count BJF ] [ 6/86 Flower Interview With a Dealer BJF 31 ] [ 91 Janik/Smith How to Deal BJ VIDEO MANUAL ] [ 22 Skills & Education Credentials for Blackjack Dealers

dealer bias. See bias.

dealer bust. When the dealer draws cards and goes over 21.  See break.

From a Simpsons Episode

Dealer Bust 21.  (DB21) (c2012) A blackjack side bet on if and how the dealer will bust.  HA = 2% – 9% depending on pay table.
[ wizardofodds.com ] [ 888casino.com ]

dealer odds. The probability of the dealer forming any given final hand according to the dealer’s up-card.  Michael Shackleford put together some excellent tables for 1 to 8 deck games and whether the dealer stood or hit soft-17.  See links below.
Dealer Odds in Blackjack under U.S. Rules ] [ Dealer Odds in Blackjack under European Rules ]

Deal or No Deal Blackjack. (c2018)  A online blackjack game by Red Tiger Gaming where the player can surrender with any initial two cards.  However, the offer given (Banker Offer) varies depending on what the player’s two cards are and what the dealer’s up-card is.  HA (base game) = 0.38%  HA (banker offer) = 4.12% (average)
[ wizardofodds.com ]

deck(s). As in a deck of cards. There are 52 cards in a regulation deck of modern-day playing cards. Four suits of ace, 2, 3, 4, 5, 6, 7, 8, 9, 10, jack, queen, and king make up a full deck. Today’s blackjack games typically use from 1 or 2 decks (hand-held) to 4,5,6, or 8 decks (dealt from a shoe). The number of decks used affects the house advantage.  Given a set of standard rules (naturals pay 3 to 2, double on any 2 cards, split to 4 hands and no re-split of aces) the house advantage changes as follows. See pack, ten.


House edge

Results above created using the Blackjack Calculator from Blackjack Apprenticeship

deck estimation. {CS} The act of estimating the number of decks (cards) left in the shoe in order to calculate a card counter’s “true count”. Different casinos may use cards of varying thickness, which might impact this estimate slightly.
[ blackjackinfo.com ] [ instagram ]

dependent trials. See independent trials.

depth charging. {CS} A single-deck strategy developed and coined by Arnold Snyder that allows the player to play a winning game without using a bet spread based on count information. Depth chargers use the depth of the deal as the primary method of gaining a long-run advantage. Depth chargers will always bet more deep in the deck, even when the count is negative. An advanced card counting system with an excellent playing efficiency is required.
[ 83 Snyder Blackbelt in Blackjack 72 ]

desirability index. (DI) Term coined by Donald Schlesinger in his book Blackjack Attack.  The higher the index number, the better the game.  The DI is a number based on a relationship between the win-rate and the standard deviation for a particular game.

Click for sample: Detroit Blackjack Team c2017Detroit Blackjack Team.  TBD See CORE Team.
[ ARCHIVE: DetroitBlackjackTeam.com 2017 ]

deuce. A playing card with a value of two (2).

Deuces WildDeuces Wild. (DW) (c2015)  An AGS blackjack side bet which is determined by the player’s first two cards.  The side bet wins if one of the player’s first two cards is a deuce, otherwise it loses.  HA ~ 5.7% – 7.3%
[ 888casino.com ]

deviations. See play variations.

device. As in an electronic or mechanical device.  See cheating.

DHMAcronym for D. Howard Mitchell.  See Edward Gordon.
[ Summer 1995 Blackjack Review 4.3: The DHM Blackjack Systems ]

DHM Expert. {PCS/L1}. (D. Howard Mitchell aka Edward Gordon) (c1973). DHM Associates, Arroyo Grande, CA. This system requires the player to count four different groups separately (low 2-5, middle 6-9, high 10, and aces). The DHM systems were once available through the Gambling Times Systems Shop. Originally based on the Gordon Count.

A 2 3 4 5 6 7 8 9 10
0 1 1 1 1 0 0 0 0 -1

BC = .86 PE = .56  IC = .85

[ 2/78 Mitchell BJ Systems From BS to Expert GT 15 ]  [ 78 Mitchell An Overview of Blackjack C&S Vol.4, 47 ] [ 80 Revere Playing Blackjack as a Business 172 ] [ 80 Snyder BJF 80 ] [ 81 Uston Million Dollar Blackjack 326 ] [ 3/84 Snyder DHM Expert Vs Uston APC BJF 16 ] [ Fall 1995 BJR 4.4: The DHM Expert ]

DHM Simplified. {PCS/L1}. (D. Howard Mitchell aka Edward Gordon) (c1974). A simplified version of DHM Professional. Originally based on the Gordon Count.

A 2 3 4 5 6 7 8 9 10
0 1 1 1 1 0 0 0 0 -1

BC = .86 PE = .56  IC = .85

DHM Professional. {PCS/L1}. (D. Howard Mitchell aka Edward Gordon) (c1974). Same as DHM Simplified but with a side count of aces.

DHM Ultimate. {PCS/L1}. (D. Howard Mitchell aka Edward Gordon) (c1978). This system is based on use of an on-line computer that is notified of every card as it is drawn. According to Mitchell, this system was inspired by the Sklansky Key Card Concept.
[ 84 Gwynn How Good Can a Pocket BJ Computer Be? ] [ 84 DHM Ultimate System Computer Simulations BJF ]

YieldOne advantage of the 2,3,4,5 low count is the effectiveness against the Over/Under 13 side bet once available in some casinos.

DI. Acronym for desirability index.

Ace of Diamondsdiamond. The red figure diamond marking one of the four suits of playing cards. See suit.
[ Wiki: Suit_(cards) ]


Diamond BlackjackDiamond Blackjack. (DD) (c2015) Also called Double Diamond Blackjack. A blackjack variant created by Gamesys N.V., a provider of software for internet casinos.  A blackjack in diamonds pays extra (2 to 1) while all other blackjacks pay even money.  Similar to Super Fun 21. (HA ~ 1.24%)
[ wizardofodds.com ] [ betvoyager.com ] [ card-counting.com ]

Digital 21Digital 21.  (D21) (c2000, 2013) aka Digital Card System or Digital Table System. An electronic casino blackjack game by DigiDeal Corp.  The game is played with digital cards (on a video display) that are electronically shuffled and dealt. MORE INFO | DATA SHEET
[ ARCHIVE: digideal.com ] [ Summer 2000 BJF  21 ]

disadvantage. See advantage.

discard holder. See discard tray.

discard tray. Also called discard holder. The plastic or metal holder used to hold the discards until the next shuffle – usually placed to the right of the dealer. The discard tray can tell the observant player how many cards have been dealt. Card counters keep a eye on this tray to determine the conversion factor required to evaluate the true count.

discards. The cards already played. See discard tray.

discipline. Control of one’s actions. Many blackjack authorities will probably tell you that self discipline is 50% (if not 75% or 95%) of the game.
[ Spr 93 Dalton Lesson 4: Discipline BJR 10 ] [ Sum 96 Dalton All Stressed Out BJR 3 ]

YieldAll the winning methods in the world are useless unless the player has the discipline to execute them accurately.

DMPro.   See Dynamic Matrix Pro Count.

DOA. Acronym for “double down on any first two cards.”  See DA. See D2.

Doc. An advantage player and card counter who posted for years on online forums as “The Doc”. Interviewed on the Gambling with an Edge podcast.
[ PODCASTS: Aug 8, 2019, Aug 15, 2019 ]

DOL. Acronym for “Discount on Loss”.  See Loss Rebate.

dollar.   Slang for $100.

Doren, Charles Van. An American writer and editor who wrote the foreword to the original edition of Playing Blackjack to Win.  Charles Van Doren was involved in the television quiz show (Twenty-One) scandal in the 1950s.

double.   See double down.

Double 21.  See Double Blackjack below.

double after split. (DAS, DBS, DS). The advantageous rule that allows the player to double down after he has split a pair. PA = +.14%

Double Attack BlackjackDouble Attack Blackjack. (DAB) (c2010) A blackjack variation, similar to Spanish 21 (no Tens are used), that allows the player to double or surrender at any time, including after splitting.  It is unique in that, the first card dealt is the dealer’s up card.  Then, players may raise or double their original bet “before” they see their cards. Blackjack pays 1:1. (HA ~ 0.62%) 
[ wizardofodds.com ] [ BlackjackInfo.com ] [ WIKIPEDIA ] [ grochowski.casinocitytimes.com ]

Double Blackjack. (2015) Michael Shackleford calls this game a cross between blackjack and pai gow poker.  It is played with a single 52-card deck.  Players make an equal 2-card and 3-card bet.  Any total under 17 or over 21 is a “fouled hand”.  There is no blackjack and rest of game is played similar to pai gow poker. An optional Double 21 side bet is also available. First offered at the Green Valley Ranch casino in Henderson, NV in November 2015. (HA for base game ~ 2.19%) (HA for Double 21 ~ 6.54%)
[ wizardofodds.com ]

double-deck. A blackjack game played with two decks and typically hand dealt. PA = -.33%  See basic strategy section.

Double Diamond Blackjack.  See Diamond Blackjack.

11 is a great double down hand!11 is a great double down hand!double down. (D, DD). The option that allows the player to double the value of his bet after looking at his first two cards. If a player doubles his bet he will receive only one additional card. Only a few casinos allow the player to double his bet after receiving more than two cards. Doubling down properly gives the player an approximate 1.5% – 1.6% gain over a mimic the dealer strategy. The following figures are the basic strategy player’s approximate losses if doubling is forbidden.

  • All soft hands = 0.1%
  • Hard 9 = 0.1%
  • Hard 10 = 0.5%
  • Hard 11 = 0.8%

If doubling is permitted on 3 or more cards the player has a gain of approximately 0.2%.

Soft Double Down Rhyme
Soft Double Down Rhyme

double down flash. (DDF) A term coined by Steve Forte to refer to a tell when the dealer intentionally flashes a face down double down card to a player.
[ 86 Forte Read the Dealer 17 ]

double down rescue. (DDR) A Spanish 21 rule term.  After doubling, if you are dissatisfied with your non-busted hand,  you may surrender. PA = +0.10%

Double Edge Blackjack. (DE) This game variation allows players to play two hands with a single wager.
[ 10/30/92 Double Edge at Edgewater, Laughlin CP ]

Vegas World Begins Double Exposure 21Double Exposure. (DBX, DX, DE) Also called Double Exposure 21, See-Thru 21 and zweikartenspiel. A game variation first introduced at Bob Stupak‘s Vegas World (October 1979) in Las Vegas in which the dealer’s hole-card is exposed. A number of other casinos in Las Vegas and Northern Nevada have typically offered this game but usually only at one or two tables. Typical rules included:

  • Dealer exposes both cards.
  • Jack & Ace of Spades pay double.
  • Player wins all blackjack ties.
  • Double downs usually restricted.
  • Dealer wins all ties except blackjack.
  • Blackjack pays even money.
  • Player may split pairs only once.

In these types of games you can generally be assured that some rules have been changed to restore to the house its overall edge. On the other hand, if you can find double exposure games with regular blackjack rules they are worth playing. See front loading.  See Exposed Hole Card Basic Strategy.  See 2 Face Blackjack.
[ WIKIPEDIA ] [ 80 Braun How to Play Winning Blackjack 161 ] [ 81 Uston Million Dollar Blackjack 40 ] [ 81 Wong Professional Blackjack 128 ] [ 81 Wong Nevada Blackjack Vol.3,75 ] [ 90 Wong Instant Update ] [ 90 Zender Card Counting for the Casino Exec. 135 ] [ wizardofodds.com ] [ PHOTO CREDIT: The Los Angeles Times ]

Double Play 21. (1992) A blackjack variation that allows the player to bet on two betting spots instead of one. The game is dealt as usual except the dealer shows two up-cards which are played out against each player’s hand respectively. First offered at the Tropicana Casino in Las Vegas in 1992.

Doublet Blackjack. (c2015) A online blackjack variation from Gamesys N.V.  In this game, the dealer has no hole card.  If the dealer gets a blackjack, then the player loses his total amount bet.  Other rules include double down rescue. (HA ~ 0.38%) Available side-bets: Sevens (HA ~ 4.09%) and Blackjack (HA ~ 5.02%)
[ wizardofodds.com ]

Double Twist Blackjack(c2016) A blackjack side bet.  Michael Shackleford estimates the house advantage on this side bet is between 3.29% (8 decks) and 4.05% (6 decks).
[ wizardofodds.com ]

double upTo increase a bet by the same amount. See press.

Double-Up-BlackjackDouble Up Blackjack (c2017) A game variation of blackjack, from TCS John Huxley, which allows players to double their initial wager after having seen their first two-cards (except if it’s a blackjack).  A dealer 16 (hard or soft) is a push, however, double-up bets lose on a push. (HA ~ 0.32%)  A side-bet is offered in this game called Bonus 16 where you get paid if you get 16 in 2 or more cards. (HA ~ 14.64%) MORE INFO
[ tcsjohnhuxley.com ] [ wizardofodds.com ]

doubling for less. To place an additional bet which is less than one’s original wager and to receive only one more card. This is usually not recommended in situations where doubling is advisable, however, money management concerns may dictate otherwise. If their bankroll is in jeopardy, players are usually recommended to consider hitting or standing before doubling for less. See double down.

Dougherty, RichardOne of Tommy Hyland team’s premier players.  According to Max Rubin, “Richard has long been one of the blackjack players casinos fear the most….and most often.  Casinos have sent out literally hundreds of flyers, bulletins, and alerts about Richard during his more than three decades as a blackjack ‘Road Warrior’ and yet he still marches on. Throughout his long, illustrious and (in)famous career, blackjack has been Richard’s virtual only source of income; no matter how many times the casinos back him off, assault him, and even go so far as to have him arrested for his legal activities, he never stops his relentless attack on their games.”  Dougherty has also won several lawsuits against casinos “after suffering through illegal ‘back roomings’ and outright beatings in front of the public on the casino floor on the Las Vegas Strip!”  A nominee for the Blackjack Hall of Fame.
[ americancasinoguide.com ] [ blackjackinfo.com ] [ bjinsider.com ]

Down Under BlackjackDown Under Blackjack. (2016)  A blackjack variation from Masque Publishing which allows the player to see the strength of the dealer’s hand before deciding how to play the hand.  After the initial deal, the dealer will identify the range of cards he has in the hold: Small (2,3,4,5) medium (6,7,8,9) or large (10,J,Q,K,A).  All hands push against a dealer 22, except for the Golden Rule: Player 21s always win against dealer 22 and original 2-card hands (no splitting) with exactly 2 Gold Cards win against dealer 22. Gold cards include 10,J,Q,K and Ace.  (HA ~ 0.57% to 1.92%) See Match the Dealer.
[ wizardofodds.com ]

Downtown. Usually a reference to downtown Las Vegas. This is the area where many Las Vegas dealers started their dealing career. It has often been classified as an area of low prestige and low tokes.
[ 80 Solkey Dummy Up and Deal 112 ]

Downtown Rules. See Las Vegas Rules.

Dracman, Frank. See Fred.

draw. As in to draw a card. See hit.

drinking. The drinking of alcoholic beverages is allowed in most casinos and usually encouraged for obvious reasons. Most casinos even offer free drinks to their customers. Don’t expect to play a winning game of blackjack and drink at the same time.  Pretending to drink at the table is a common camouflage technique for card counters.  Buy (or bring) a dark glass bottle of beer, empty the contents, fill it with water and pretend to drink it at the table.  A glass of apple juice on the rocks also does the trick 🙂

drop. A casino management term for the total amount of money in cash or markers that players have used for the purchase of chips at a casino table. See drop box. See hold.

drop box. A box, locked to the underside of a blackjack table, into which the dealer deposits all currency.

drop cut. The dealing technique of holding a stack of chips in one hand and touching them to the table. The dealer then lifts some of them, leaving a small stack of the precise number of chips wanted.
[ 80 Solkey Dummy Up and Deal 112 ]

Dr. Pepper Rule.  See Rule of 10, 2, 4.

DS. Acronym for double after split.

DS10. Acronym for double on a ten or 11 after splitting..

DSA. Acronym for double after split aces.  See DACE.

DTS. Acronym for Digital Table System. See Digital 21.

Harvey DubnerDubner, Harvey Alan.  (July 14, 1928 – Oct 23, 2019) An engineer and mathematician who published a paper on the first blackjack point count system (High-Low) which is used by many blackjack card counters today. This was presented at the Fall Joint Computer Conference held in Las Vegas on Nov 13, 1963 at 8PM, at a panel titled “Using Computers in Games of Chance and Skill“.  Dubner is also credited for his contributions in finding large prime numbers.  In 1993, he was responsible for more than half the known primes of more than two thousand digits.
[ WIKIPEDIA ] [ WIKISAGE ] [ 17 Golden Never Split Tens App IV ] [ Harvey Dubner and the Hi-Lo Strategy ] [ encyc.org ] [ alchetron.com ] [ dblp.uni-trier.de ]

Dubner Hi-Low. {PCS/L1}. (Harvey Dubner) (c1963). See Hi-Lo.

Duel 21 Blackjack.  (aka 21 Duel Blackjack) (2017) A online blackjack variant from Playtech..  Play includes making an Ante bet (HA ~ 0.16%) and an optional 2 Up side bet (HA ~ 6.53%).  See link below for more information.
[ wizardofodds.com ]

Semyon DukachDukach, Semyon.  (aka  Nikolay Nogov)  (Born Oct 25, 1968) Former professional blackjack player and member of the MIT Blackjack Team.  Some of Semyon’s exploits are written about in Mezrich’s second book on the subject called Busting Vegas.  Founder of the Blackjack Science web site.
[ WIKIPEDIA ] [ ARCHIVE: blackjackscience.com ] [ History VS Hollywood ]

dummy up. As in dummy up and deal. An oral command given by a pit boss to a dealer, telling the dealer to stop chatting with the players.
[ 80 Solkey Dummy Up and Deal ]

Eleanore DumontDumont, Eleanore.  (aka Madame Mustache and Simone Jules)  (c1829-Sept 8, 1879) In 2006, Eleanore Dumont was nominated for the Blackjack Hall of Fame.  According to the ballot information, “… she was the first known professional twenty-one player in history. Throughout a gambling career of almost thirty years, Madame Mustache played only one game—twenty-one—and in the gambling dens of the old West (c1860s), she became a legend in her lifetime.” 
[ ARCHIVE: blackjackforumonline.com ] [ legendsofamerica.com ]

dump. To lose a large amount of money quickly. See dumping table.

dumping table. A casino term referring to a table where the players have been winning excessively. 

Dunbar. Author of Dunbar’s Risk Analyzer for Blackjack.  Dunbar won the Munchkin Award at the 2020 Blackjack Ball.

Dusty. A card counter who was part of the Church Team.  Interviewed on the Gambling with an Edge podcast.
[ PODCAST: Apr 18, 2014 ]

DX. Acronym for Double Exposure.   See DE.  See DBX.

Dylag Card Counting Prevention Apparatus. See blackjack shields.

Dynamic Matrix Pro Count.  (DMPro) {PCS/L3}. (Maverick Sharp) (2013). A balanced level-3 count described in the book Dynamic Blackjack. This is essentially Wong’s Halves count doubled.

 A 2 3 4 5 6 7 8  9 10
 -2 1 2 2 3 2 1 0 -1 -2 

BC = .99 PE = .57  IC = .72




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