Overview
In poker, bad beat is a subjective term for a hand in which a player with what appear to be strong cards nevertheless loses. It most often occurs where one player bets the clearly stronger hand and their opponent makes a mathematically poor call that wins with any subsequent dealing to complete the hand.
In pure mathematical terms a one-outer can be considered a pure bad beat, however there is no consensus among poker players as to what else exactly constitutes a bad beat and often players will disagree about whether a particular hand was a bad beat. A few examples are: quads over full house, quads over quads, straight flush over quads, small full house vs. bigger full house or better.
Types of bad beats
Virtually any hand that looked like a favorite to win can end up losing as more cards are dealt, but bad beats usually involve one of two not mutually exclusive scenarios:
The player who wins on a bad beat is rewarded for mathematically unsound play. Calling a bet despite having neither the best hand nor the right pot odds or implied odds to call, then winning anyway, is characteristic of this type of bad beat. It can also involve the inferior hand catching running cards when it requires two cards in a row to come from behind to win the pot. For example, catching cards on both the turn and the river in Texas hold 'em that complete a straight or flush.
A very strong hand loses to an even stronger one, better known as "cooler". This type of beat occurs with some frequency in movies. In the films The Cincinnati Kid and Casino Royale, The Kid and Le Chiffre, respectively, each lose with a full house to a straight flush. In this situation, it is possible that both players have played their cards well, and avoiding the bad beat could not have been achieved without committing a mistake.
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