knock·​out | \ ˈnäk-ˌau̇t How to pronounce knockout (audio) \

Definition of knockout

 (Entry 1 of 3)

1a : 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



Definition of knockout (Entry 2 of 3)

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

knocked out; knocking out; knocks out

Definition of knock out (Entry 3 of 3)

transitive verb

1 : to produce roughly or hastily
2a(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
See More
Recent Examples on the Web: Noun East Los Angeles remained undefeated and retained her WBA minimumweight title with a stirring fourth-round knockout of Maria Santizo (9-1, 5 KOs) of Guatemala. John Whisler, San Antonio Express-News, 19 Dec. 2021 Because as exhilarating as Garcia’s seventh-round knockout of Campbell was, the fight also confirmed suspicions about his shortcomings. Dylan Hernández Columnist, Los Angeles Times, 3 Jan. 2021 Highlight reels and knockout memes capture fighters' at their worst–or best–but miss their nuance. Brian Roberts, Forbes, 27 Dec. 2021 In this season of giving, both fighters delivered a memorable punching performance that ended, predictably, in a knockout. John Whisler, San Antonio Express-News, 19 Dec. 2021 President Biden’s tax and entitlement plan received what should be a pair of knockout punches late last week. The Editorial Board, WSJ, 12 Dec. 2021 Eight teams that placed third in Champions League groups enter a separate draw on Monday for the Europa League knockout playoffs in February. Graham Dunbar, ajc, 9 Dec. 2021 Because despite the downplaying of some series officials, IndyCar is knocking on the door of a significant part of its CART past: knockout qualifying in more races than the Indianapolis 500. Nathan Brown, The Indianapolis Star, 8 Dec. 2021 His knockout streak ended at 16 bouts, possibly because of the hand injury and largely because Cruz, 23, from Mexico City, applied steady pressure and did not buckle under Davis’s thunderous punches. New York Times, 6 Dec. 2021 Recent Examples on the Web: Adjective Quarterback Matthew Stafford passed for 309 yards, including a go-ahead touchdown with 57 seconds remaining, and the Los Angeles Rams held on late for a 20-19 win in Baltimore, dealing a nearly knockout blow to the Ravens’ playoff hopes. Jonas Shaffer,, 2 Jan. 2022 The Jubilant Collection contains essentials for hosting a knockout New Year’s Eve celebration (just add Champagne). Megan Murphy, Robb Report, 21 Dec. 2021 Buster must hatch a knockout concept to impress Jimmy Crystal (Bobby Cannavale), the gangsterish — and rather insane — white wolf and owner of Redshore’s Crystal Tower Theater, who’s seeking the ultimate show for his glamorous venue. Gary Goldstein, Los Angeles Times, 21 Dec. 2021 Under their labor contract, U.S. men got $55,000 each for making the 2014 World Cup roster, then split $4.3 million for earning four points in the group stage and reaching the knockout stage. oregonlive, 13 Dec. 2021 The club also failed to reach the knockout stage of the Champions League. Manuel Veth, Forbes, 9 Dec. 2021 Only 15 of the 16-team lineup in the knockout stage were known on Wednesday night. Graham Dunbar, ajc, 9 Dec. 2021 Visitors are invited to strike a pose in the photo- booth for a knockout #HERMESFIT moment. Allyson Portee, Forbes, 5 Nov. 2021 Jenkins’ 1970s-style production takes a while to get going but once this knockout crew of sisters take the stage, the show becomes a total blast. Chris Jones,, 12 Nov. 2021

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'knockout.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of knockout


1887, in the meaning defined at sense 1a


1818, in the meaning defined at sense 1


1856, in the meaning defined at sense 1

Learn More About knockout

Time Traveler for knockout

Time Traveler

The first known use of knockout was in 1818

See more words from the same year

Dictionary Entries Near knockout

knock on the door of


knock out

See More Nearby Entries 

Statistics for knockout

Last Updated

4 Jan 2022

Cite this Entry

“Knockout.” Dictionary, Merriam-Webster, Accessed 21 Jan. 2022.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

More Definitions for knockout



English Language Learners Definition of knockout

 (Entry 1 of 2)

: an occurrence in which a boxing match ends when a fighter has been knocked down by a punch and is unable to start fighting again before 10 seconds have passed
: a very attractive or appealing person or thing



English Language Learners Definition of knockout (Entry 2 of 2)

: causing someone to become unconscious
: extremely attractive or appealing
: designed so that winning teams or players continue to play and losing teams or players do not


knock·​out | \ ˈnäk-ˌau̇t How to pronounce knockout (audio) \

Medical Definition of knockout

: 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

Nglish: Translation of knockout for Spanish Speakers

Britannica English: Translation of knockout for Arabic Speakers Encyclopedia article about knockout


Test Your Vocabulary

Difficult Spelling Words Quiz

  • alphabet pasta spelling help
  • Which is the correct spelling?
Name That Thing

Test your visual vocabulary with our 10-question challenge!

Universal Daily Crossword

A daily challenge for crossword fanatics.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!