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
Aleks Klosok, CNN Money, 6 May 2026
The aim wasn’t a knockout, but the gradual deterioration of San Antonio.
—Marcus Thompson Ii, New York Times, 5 May 2026
Pete Hammond, Deadline, 30 Apr. 2026
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
ABC News, 6 May 2026
Tuesday will test whether Arsenal can convert that reward, at the same stage where they were knocked out last year.
—Sukhman Singh, New York Times, 5 May 2026
See All Example Sentences for knockout
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Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
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Noun
The Parisians struggled at the start of this season’s campaign, needing a playoff to reach the knockout rounds.
—Aleks Klosok, CNN Money, 6 May 2026
The aim wasn’t a knockout, but the gradual deterioration of San Antonio.
—Marcus Thompson Ii, New York Times, 5 May 2026
Adjective
The next day all anyone could talk about on that show was the knockout and sultry performance from this unknown new star.
—Pete Hammond, Deadline, 30 Apr. 2026
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
Verb
Alabama Republicans, too, are forging ahead with plans to knock out at least one of two Democratic seats, even though the state is under court order to use its current map until 2030.
—ABC News, 6 May 2026
Tuesday will test whether Arsenal can convert that reward, at the same stage where they were knocked out last year.
—Sukhman Singh, New York Times, 5 May 2026
See All Example Sentences for knockout
Cite this Entry
“Knockout.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/knockout. Accessed 8 May. 2026.
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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