Bad beat
Losing a pot as a big favorite
Definition
A bad beat is losing a pot in which you were a heavy favorite when the money went in: AA cracked by 7♠6♠ hitting a runner-runner flush, a set outdrawn by a gutshot on the river. The more improbable the comeback, the worse the beat. Mathematically, a bad beat is great news in disguise: it means you got the money in with the edge — exactly what you're trying to do on every hand. A player who takes bad beats regularly is a player who dominates opponents when the big pots happen. The opposite (winning as the underdog) is called a suckout, and it's the sign of playing big pots badly. Emotional management makes all the difference: the bad beat is the number one tilt trigger. The reflex to build is judging every hand on the quality of the decision, never on the result. Some rooms offer "bad beat jackpots" that reward very strong losing hands — strategically anecdotal, but revealing: losing with quads is rare enough to earn a bonus.
You get all-in preflop with A♠A♥ against Q♣J♣ (~80% equity in your favor). Flop K♣T♦4♣, turn 9♣: opponent's straight and flush draws get there — you lose the hand. It's a bad beat: the decision was perfect, the result bad. Replay this spot 100 times and you win about 80 of them.