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
Matt Woosnam, New York Times, 28 May 2026
Gillette, rebranded as Boston Stadium, is set to host seven matches – five in the group stage and two knockout games – between June 13 and July 9.
—Lance Reynolds, Boston Herald, 27 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
Jason Green, Mercury News, 29 May 2026
But Bodo/Glimt knocking out last season’s finalists Inter was amazing too.
—Jack Lang, New York Times, 28 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
Even the subsequent progress beyond Zrinjski and AEK Larnaca in the knockout stages felt vaguely underwhelming, as teams continued to sit deep and clog up the play.
—Matt Woosnam, New York Times, 28 May 2026
Gillette, rebranded as Boston Stadium, is set to host seven matches – five in the group stage and two knockout games – between June 13 and July 9.
—Lance Reynolds, Boston Herald, 27 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
Four people have been arrested and charged in connection with a utility wire theft that caused $50,000 in damage and knocked out telecom services for 10,000 customers in Fremont, police said.
—Jason Green, Mercury News, 29 May 2026
But Bodo/Glimt knocking out last season’s finalists Inter was amazing too.
—Jack Lang, New York Times, 28 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 29 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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