In blackjack, "bust" refers to a situation where a player's hand exceeds the total value of 21, resulting in an automatic loss for that hand. This can occur when the player takes additional cards and the total surpasses 21. When a player busts, they forfeit their bet, regardless of the dealer's hand. The term is crucial in blackjack, as avoiding a bust is a key part of the strategy, with players needing to carefully decide when to hit or stand to protect their hand from going over 21.