/ ˈnɒkaʊt; NAmE ˈnɑːk-/ noun , adjective
■ noun
1.
( abbr. KO ) ( in boxing ) a blow that makes an opponent fall to the ground and be unable to get up, so that he or she loses the fight
2.
( informal ) a person or thing that is very attractive or impressive
■ adjective [ only before noun ]
1.
( especially BrE ) a knockout competition is one in which the winning player / team at each stage competes in the next stage and the losing one no longer takes part in the competition :
the knockout stages of the tournament
2.
a knockout blow is one that hits sb so hard that they can no longer get up