Bad BeatA bad beat is a hand in which a player whose hand was highly favoured is beaten in an improbable turn of events. The boundary between a regular beat and a bad one varies from player to player. It's is generally thought that a winning hand whose chances of winning were around 5-10% is a bad beat, or if a player wins by hitting two perfect cards.
Here is an example of a bad beat in Texas Hold'em:
|Player A||Player B|
Suckout, Cooler, Cold Deck, Draw