1
a
: the act of knocking out : the condition of being knocked out
b(1)
: the termination of a boxing match when one boxer has been knocked down and is unable to rise and resume boxing within a specified time
c
: a blow that knocks out an opponent
2
: a sensationally striking, appealing, or attractive person or thing

knockout

2 of 3

adjective

1
: causing a knockout
a knockout blow
2
: sensationally striking, appealing, or attractive
a knockout dress
3
: having all or part of a gene eliminated or inactivated by genetic engineering
knockout mice predisposed to diabetes mellitus

knock out

3 of 3

verb

knocked out; knocking out; knocks out

transitive verb

1
: to produce roughly or hastily
2
a(1)
: to defeat (a boxing opponent) by a knockout
(2)
: to make unconscious
the drug knocked him out
b
: to make inoperative or useless
electricity was knocked out by the storm
c
: to get rid of : eliminate
knocked out illegal gambling
3
: to tire out : exhaust
knocked themselves out with work
4
: to cause (an opposing pitcher) to be removed from a baseball game by a batting rally

Examples of knockout in a Sentence

Noun He won the match by a knockout. He scored a knockout in the fourth round. She's a real knockout in that dress.
Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Noun
Of his 21 career wins in MMA, 13 came via knockout. Dj Siddiqi, Forbes.com, 1 Aug. 2025 The midweek matchup will be the first meeting between these teams, with each aiming to secure a top-four finish in their respective groups to advance to the knockout stages of the competition. Ben Verbrugge, MSNBC Newsweek, 31 July 2025
Adjective
Since the tournament became a solely knockout competition in 2018, home teams have won exactly 54% of matches over 90 minutes. Ian Nicholas Quillen, Forbes.com, 31 May 2025 Arteta understandably is more risk-averse in knockout European ties, but Premier League matches sometimes need to be forcibly opened up — even at the risk of fatigue or becoming defensively compromised. Liam Tharme, New York Times, 13 Apr. 2025
Verb
How can the Bills finally get over the hump against the Chiefs? Buffalo has been knocked out of the playoffs four times by the Chiefs, and that’s why Allen hears the question so frequently. Pete Grathoff, Kansas City Star, 30 July 2025 Plunkett’s Unicorns were knocked out in the play-offs by eventual winners MI New York. Nick Miller, New York Times, 29 July 2025 See All Example Sentences for knockout

Word History

First Known Use

Noun

1887, in the meaning defined at sense 1a

Adjective

1818, in the meaning defined at sense 1

Verb

1856, in the meaning defined at sense 1

Time Traveler
The first known use of knockout was in 1818

Browse Nearby Words

Cite this Entry

“Knockout.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/knockout. Accessed 13 Aug. 2025.

Kids Definition

knockout

1 of 2 noun
1
: the act of knocking out : the condition of being knocked out
2
: something or someone very striking or attractive
knockout adjective

knock out

2 of 2 verb
ˈnäk-ˈau̇t,
näk-ˈau̇t
: to make unconscious

Medical Definition

knockout

adjective
: having all or part of a gene eliminated or inactivated by genetic engineering
knockout mice predisposed to diabetes mellitus serve as animal models in the study of human diabetes

More from Merriam-Webster on knockout

Last Updated: - Updated example sentences
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