knock·out
ˈnäk-ˌau̇t 
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
(2)
c
: a blow that knocks out an opponent
2
: a sensationally striking, appealing, or attractive person or thing
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
knocked out; knocking out; knocks out
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.
Adjective
The Wimbledon tennis tournament is a knockout competition.
a knockout sports car that's the talk of the neighborhood
Verb
the entire staff knocked itself out getting the project finished on time
Recent Examples on the Web
Chris Biderman, Sacbee.com, 7 Dec. 2025
In another, a knockout image featuring two children resting on their backs, sunlight blazes with an almost divisive intent, turning one child’s eyeglasses opaque with its glare while leaving his friend’s face in shadow.
—Dawn Chan, New Yorker, 6 Dec. 2025
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
Ryan Gaydos, FOXNews.com, 9 Dec. 2025
That includes knocking out the porch windows, removing most of the kitchen appliances, and reconstructing the furniture pieces.
—Francesca Pica, jsonline.com, 9 Dec. 2025
See All Example Sentences for knockout
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Noun
Additionally, the first knockout round is the Round of 32, which means the top two teams from each group advance past the group stages and the eight best third-place teams move on, based on points, goal differential, goals scored, discipline (card points) and FIFA ranking.
—Chris Biderman, Sacbee.com, 7 Dec. 2025
In another, a knockout image featuring two children resting on their backs, sunlight blazes with an almost divisive intent, turning one child’s eyeglasses opaque with its glare while leaving his friend’s face in shadow.
—Dawn Chan, New Yorker, 6 Dec. 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
Instead, the ball was knocked out of his hands.
—Ryan Gaydos, FOXNews.com, 9 Dec. 2025
That includes knocking out the porch windows, removing most of the kitchen appliances, and reconstructing the furniture pieces.
—Francesca Pica, jsonline.com, 9 Dec. 2025
See All Example Sentences for knockout
Cite this Entry
“Knockout.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/knockout. Accessed 12 Dec. 2025.
Copy CitationKids Definition
knockout
1 of 2 noun
knock·out
ˈnäk-ˌau̇t
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 verbˈnäk-ˈau̇t,
näk-ˈau̇t
: to make unconscious
Medical Definition
knockout
adjective
knock·out
ˈnäk-ˌau̇t
: 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
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