A technical knockout or TKO occurs when a boxer is deemed unfit to continue and the referee ends the bout. This may be to protect a boxer who is being unduly punished by his opponent or as a result of injury such as a bad cut, broken nose or jaw.
The referee is the only official who can declare a TKO but he might consult the ring doctor for his opinion. Sometimes the boxer's corner, second, trainer or manager may ask the referee to stop it, throw in the towel or the boxer himself may quit on his own volition.
A technical knockout ends the bout, and results in a TKO win for the boxer's opponent (a TKO counts towards the "knockout" total in a boxer's fight record). This type of stoppage is also known as Referee Stops Contest / RSC or as a Technical Count Out / TCO.