A bad beat in poker 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, but 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.

According to Poker.org, a bad beat is when you have one of the statistically strongest poker hands possible but it still turns out to be the losing hand. Bad beats are commonly depicted in high-stakes cash games and poker tournaments in movies and television shows because they offer heightened drama. However, what is actually considered a bad beat hand is usually fairly subjective. For example, newer poker players who are overly confident in their hands may believe they had a bad beat, but in fact, their hand was never particularly strong to begin with.

In summary, a bad beat in poker is when a player loses a hand despite having strong cards, often due to a mathematically poor call by their opponent. The definition of a bad beat can be subjective, and players may disagree about whether a particular hand qualifies as a bad beat.