In gambling, the term "proposition bet" (prop bet, prop, exotic, novelty, or a side bet in the first context below) has two definitions.
In most contexts, "proposition bet" denotes a bet made regarding the occurrence or non-occurrence during a game (usually a gambling game) of an event not directly affecting the game's final outcome. Proposition bets in sports are differentiated from the general bets for or against a particular team or regarding the total number of points scored. Traditionally, proposition bets can be made on outcomes such as the number of strikeouts a pitcher will accumulate in a baseball game, whether a non-offensive player will score in an American football game, or which team will score the first points of the game. Examples include:
- Betting on which specific sub-outcomes occur during a game in which multiple sub-outcomes normally have the same value, for example:
- Betting on the number of balls/strikes thrown by an American baseball pitcher, which is where the proposition bet was said to have originated.
- Betting on which team scores first in a match
- Betting on the specific face value of one or more individual dice in craps
- Betting on which cards will make up the flop in a hand of poker
- Betting on which cards are dealt in blackjack: Over 35 different blackjack side bets are widely recognized in casinos. On some bets, such as the "Lucky Ladies" side bet that wins only if the first two cards dealt to a player equal 20. These bets are rarely favored by experienced gamblers as the house edge on them typically exceeds the edge in a normal game. For example, the "Super 7s" side bet in blackjack has a house edge of 12.6, while blackjack itself has a house edge of around 1% if the player follows basic strategy. There are side bets however that have very low house advantages such as "The 18 Bet" at the Eureka Casino in Mesquite which is almost under 2%.
- Betting on specific aspects of the pageantry surrounding a sporting event, such as a) the duration of the word "brave" in the pregame performance of the U.S. national anthem or b) the color of the Gatorade or other sports drink dumped on the winning team's coach in the traditional practical joke and victory ritual known as Gatorade shower
- The Nevada Gaming Commission does not allow casinos to offer any type of non-sport related proposition bets although these kinds of prop bets can often be found online.
Less commonly, "proposition bet" (in this context also "one-of-a-kind bet") denotes a dare for money; phrased in terms of the above definition, the bet is on whether the "dared" person will make a given event happen. If the "dared" person accepts the bet, he will collect if he succeeds or pay if he fails.
For an example detailed in the book The Professor, the Banker, and the Suicide King, David Grey once bet Howard Lederer, a professional poker player who became vegetarian following gastric bypass surgery, $10,000 that Lederer would not eat a cheeseburger. Lederer accepted the wager, ate the cheeseburger, and won the bet.