Informal. a person or thing overwhelmingly attractive, appealing, or successful.
5.
a panel in a casing, can, or box, especially of metal or plastic, so designed that it can readily be removed, as by punching, hammering, or cutting, to provide an opening into the interior:
a knockout in a junction box.
6.
Machinery. a device for knocking something loose, as finished work from a lathe chuck.
adjective
7.
that knocks out:
the knockout punch.
Origin
1810-20;1935-40for def 4; noun, adj. use of verb phrase knock out
Examples from the web for knockout
One of the knockout pieces on display is of one of the more recognizable people in the struggle for civil rights.
He lost his biggest fight because he had to go for a knockout instead of playing it smart.
The diabetic mouse model has not always translated well to humans, and commonly used knockout mice represent an extreme condition.
knockout mice, which completely lacked the gene and so manufactured no mu opiate receptors, were all the more sensitive.
And so each place you have got this different knockout, basically mutation.
And the knockout punch is finding out that he's not real at all.
Before long, the knockout mice began developing curious lesions around their mouths.
The winner is determined by knockout, checkmate, or referee decision.
Plenty of daunting chores await the job hunter, from writing a knockout resume to acing an interview.
Double knockout a team event that requires two losses for elimination.
British Dictionary definitions for knockout
knockout
/ˈnɒkˌaʊt/
noun
1.
the act of rendering unconscious
2.
a blow that renders an opponent unconscious
3.
a competition in which competitors are eliminated progressively
(as modifier): a knockout contest
4.
a series of absurd invented games, esp obstacle races, involving physical effort or skill
5.
(informal) a person or thing that is overwhelmingly impressive or attractive: she's a knockout
verb (transitive, adverb)
6.
to render unconscious, esp by a blow
7.
(boxing) to defeat (an opponent) by a knockout
8.
to destroy, damage, or injure badly
9.
to eliminate, esp in a knockout competition
10.
(informal) to overwhelm or amaze, esp with admiration or favourable reaction: I was knocked out by that new song
11.
to remove the ashes from (one's pipe) by tapping
Word Origin and History for knockout
n.
also knock-out, in fighting, 1887, from verbal phrase knock out "to stun by a blow for a 10-count" in boxing, short for to knock out of time; see knock (v.) + out. Slang meaning "attractive person" is from 1892. To knock oneself out "make a great effort" is from 1936.
Slang definitions & phrases for knockout
knockout
modifier
: That was a knockout plot/ a knockout wife and two daughters
noun
An especially attractive person or thing; dish: Saaay, you know, you're a knockout(1906+)