THE ENCYCLOPEDIA OF CASINO TWENTYONE
# A B C D E F G H I J K L M N O P Q R S T U V W XYZ
OBBO. Acronym for dealer takes “Original and Busted Bets Only”. If players are forced to play out hands before the dealer checks for blackjack then this is one of several rule options available. Under OBBO rules, if the dealer ends up with a blackjack, the dealer takes any busted bets and one unit from each unbusted hand on the table. This is a very unfavorable rule for players. Players are at risk to lose additional bets from splitting. See OBO. See ENHC. See BB+1. See No Hole Card Basic Strategy.
[ https://wizardofodds.com/games/australianblackjack/ ]
object of the game. The object of the game of twentyone, also known as blackjack, is to beat the dealer. This is accomplished by obtaining a hand that totals higher than that of the dealer, but not greater than 21. It can also be accomplished by having the dealer bust or go over 21. If the player busts before the dealer then the player automatically loses even if the dealer subsequently busts as well. See Rules of the Game.
OBO. Acronym for dealer takes “Original Bets Only”. If players are forced to play out hands before the dealer checks for blackjack then this is one of several rule options available. OBO is the most favorable and typical of most USA casinos. See OBBO. See ENHC. See BB+1.
[ https://wizardofodds.com/games/australianblackjack/ ]
odds. Chance can be expressed either as a probability or as odds. Odds are defined as the probability that an event will occur divided by the probability that the event will not occur. In blackjack analysis, we typically prefer the use of probabilities. See probability.
How to convert from odds to probability:

offthetop. The first hand of a new deck or shoe immediately after the shuffle.
Ohio. In 2016, Ohio had 5 casinos with over 250 blackjack tables.
[ https://www.qfit.com/maps.shtml ]
Oklahoma. In 2016, Oklahoma had 10 casinos with 111 blackjack tables.
[ https://www.qfit.com/maps.shtml ]
Olsen, Eddie. Coauthor of the book Break the Dealer and original developer of the TARGET system. Publisher and editor of Blackjack Confidential magazine for 18 years. Olsen is also an avid artist.
[ http://www.eddieolsenartworks.com ]
Olsen TruCount {PCS/L2}. (Eddie Olsen) (1991) An unbalanced card counting system developed by Eddie Olsen with original computer system analysis by Michael Dalton.
A 2 3 4 5 6 7 8 9 10
1 1 1 1 2 1 * 0 * 1
* Red or Black 7s count 1
Red or Black 9s count 1
BC = .96 PE = .52
[ 1012/91 Olsen Blackjack Confidential ]
[ 91 Olsen The Olsen TruCount ]
Omega II. {PCS/L2}. (Bryce Carlson) (1992) An advanced balanced point count system. See Canfield Master.
A 2 3 4 5 6 7 8 9 10
0 1 1 2 2 2 1 0 1 2
BC = .92 PE = .67 IC = .85
[93 Carlson Blackjack For Blood]
oneway deck. According to Wikipedia, a oneway deck is a deck of playing cards where the back of the cards has a pattern which can be oriented to have a “top” and “bottom”. Magicians and card sharps can use the orientations of cards in oneway decks to encode information that allows them to perform card tricks
[ https://en.wikipedia.org/wiki/Oneway_deck ]
OPP Card Counting System. {PCS} (2005) Carlos Zilzer. A simpler card counting system where the player only counts the number of low cards dealt per round and compares this with the number of hands played in the round. The rules of OPP are:
 A hand with no low cards (2 – 6) has a value of 1
 A hand with one low card has a value of 0
 A hand with 2 low cards has a value of +1
 A hand with 3 low cards has a value of +2 and so on
 Split hands are considered new hands
[ http://www.blackjackforumonline.com/content/card_counting_technique_easyOPP.htm ]
opposition betting. {CS}. This is a multideck betting strategy where the player waits for the count to turn down before raising a bet. Originally intended as a way to cover a bet spread.
[83 Snyder Blackbelt in Blackjack 85]
[90 Patterson Blackjack: A Winner’s Handbook 103]
[90 Patterson Count Reversal Strategy WIN 62]
optimal betting theory. See Kelly Criterion.
Oregon. In 2016, Oregon had 8 casinos with 73 blackjack tables.
[ https://www.qfit.com/maps.shtml ]
Oscar’s Grind. {PBS} The goal of this system is to win one betting unit for each series of bets. First bet is 1 unit. If lost the next bet is also 1 unit. After each successive loss the next bet is always the same size as the bet just lost. When a series is losing the proceeds of a won bet are used to increase the next bet by one unit. No bet should ever be larger than necessary to end a series with a profit of one unit.
[79 Ainslie How to Gamble in a Casino 74]
[70 Wilson The Casino Gambler’s Guide]
OSR. See Overall System Rating.
OU or O/U. See Over/Under 13.
out shuffle. See perfect shuffle. See in shuffle.
[03 Poolside The Poolside Report: Blackjack Ace Tracking]
outfielder. A team player who is not seated.
Overall System Rating. (OSR) A combined rating which includes betting correlation, playing efficiency, and the insurance correlation.
[99 Reid http://www.bjmath.com/bjmath/counting/OSRating.htm ]
Over/Under 13. (OU or O/U) An optional side bet first introduced in 1988 at Caesars Tahoe in Stateline, Nevada that allows the player to wager on his original 2 cards as to whether they will total over 13 or under 13. The developer, Ken Perrie, a Caesars pit boss, owns the rights to the design of the unique table layout used. Typical rules have been:
 No requirement to play over/under.
 Wager based on original two card hand.
 Not to exceed wager on blackjack hand.
 Even money pays on win.
 Aces count as 1 only.
 Face cards count as 10.
 Must have wager on blackjack hand to make Over/Under 13 bet.
 House wins any 2 card totals of exactly 13.
Basic strategy for the over/under bet is to never take it. A modified counting system is required to take advantage of the excellent profit potential in this game. A typical card count that would be effective for detecting favorable opportunities for this bet is:
A 2 3 4 5 6 7 8 9 10
1 1 1 1 0 0 0 0 0 1
BC = .59 PE = .47 <– Regular blackjack play only
As can be seen from the BC and PE above this count would be ineffective for regular blackjack play.
HA = +6.56% (over)
HA = +10.06% (under)
[89 Snyder The Over/Under Report] [89 Snyder Inside the Over/Under BJF] [12/89 Snyder The Over/Under Spreads BJF] [12/89 Wong Current Blackjack News] [3/90 Snyder Over/Under Goes Over BJF] [3/90 Smallwood Crushing the O/U Bet BJM 8] [9/90 Snyder Over/Under Update BJF] [90 Chambliss Fundamentals of Blackjack 67] [7/91 Olsen Ken Perrie – An Innovator on the… BJC] [9/92 Schlesinger Lost in the Maze of New Rules BJF] [ https://www.blackjackreview.com/wp/catalog/blackjackreports/ ] [ http://www.blackjackforumonline.com/content/Over_Under_Card_Counting_System.htm ] [ https://www.qfit.com/cvblackjackhelp/overunderstrategy.htm ]
Owens, Griffith K. See Lawrence Revere.