knockout

1. (informal) Something wildly popular, entertaining, or funny.Examples: "If you've ever had a sack race, you know it's a real knockout for kids and adults alike."informal

2. (informal) A very attractive person, especially a beautiful woman.Examples: "Phrases such as "she bowled me over," "she's striking," and "she's a knockout" suggest that the woman affects the man in ways he cannot mediate or control."; "She was the "bikini-babe", "Sarkozette" stunna who never was. Paris was baffled this week when some of the British media began drooling over an old beach photograph of a former newsreader, Christine Kelly, whom they announced as Sarkozy's latest cabinet appointment—or rather "knockout lovely" or "oh yes, minister!"."Synonyms: stunnerinformal

3. (genetics) The deactivation of a particular gene.

4. (genetics) A creature engineered with a particular gene deactivated.

5. (printing) An event where a foreground color causes a background color not to print.

6. (sports) A tournament in which a team or player must beat the opponent in order to progress to the next round.Examples: "the knockout stages of the competition"; "In truth, Tottenham never really looked like taking all three points and this defeat means they face a battle to reach the knockout stages -with their next home game against PAOK Salonika on 30 November likely to prove decisive."