A TKO, or Technical Knockout, occurs in combat sports like boxing and mixed martial arts when a fighter is unable to continue the match due to the referee's decision. This can happen if one fighter is dominating the other, causing significant damage or if the opponent is unable to defend themselves effectively. In a TKO situation, the referee steps in to stop the fight, ensuring the safety of the fighters. This decision can be based on a fighter's inability to respond to their opponent's attacks or if their corner throws in the towel, signaling they want to end the match.