in·​fest | \in-ˈfest \
infested; infesting; infests

Definition of infest 

transitive verb

1 : to spread or swarm in or over in a troublesome manner a slum infested with crime shark-infested waters

2 : to live in or on as a parasite

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Other Words from infest

infestant \ in-​ˈfe-​stənt \ noun
infestation \ ˌin-​ˌfe-​ˈstā-​shən \ noun
infester \ in-​ˈfe-​stər \ noun

Synonyms for infest



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Examples of infest in a Sentence

in desperation, we called in an exterminator because the house was infested with ants

Recent Examples on the Web

The twist is that the map is also infested with cube monsters that are trying to kill you. Andrew Webster, The Verge, "Fortnite’s cube monsters aren’t gone just yet," 6 Nov. 2018 MacDonald described a crop that was infected with powdery mildew from the beginning and later was infested with spider mites and other pests. Michael Dresser, Washington Post, "Regulators investigate Maryland medical marijuana grower for alleged pesticide use," 10 July 2018 From a black widow found in store bought broccoli to a Tennessee woman who claims her apartment is infested with dozens of brown recluse spiders, these eight-legged creatures can be found just about anywhere. Madeline Farber, Fox News, "Brown recluse, black widow and other dangerous spiders found in the US," 10 July 2018 The dogs — mostly Lab mix pups — also appeared to be malnourished and infested with fleas. Kaitlyn Schwers, kansascity, "They left 13 dogs in a hot car for hours, Missouri cops say. Now they face charges," 31 May 2018 The San Francisco Fire Department found 20 people living in rooms infested with rats and roaches in the basement of a three-story building in the Outer Mission neighborhood in 2016. Dominic Fracassa, San Francisco Chronicle, "SF settles with owner, landlord of Outer Mission building called “death trap”," 17 May 2018 That’s why the Chagos are a perfect place to study the impact of rats—which have infested 90 percent of the globe’s island groups—on bird populations. Jason Daley, Smithsonian, "Coral Reefs Need Fewer Rats and More Bird Poo," 12 July 2018 Small hive beetles also can infest a colony, destroying the structure of the hive itself and spoiling the honey. Kevin Davenport, idahostatesman, "Why are these 250,000 bees hanging out on this sweet Downtown Boise rooftop?," 11 July 2018 The rusted silos are infested with mosquitoes; there’s no grain inside or livestock nearby., "Prisonville, Texas, Hopes to Reboot Its Economy on the Back of Trump’s Immigration Crackdown," 28 June 2018

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

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First Known Use of infest

1602, in the meaning defined at sense 1

History and Etymology for infest

French infester, from Latin infestare, from infestus hostile

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Statistics for infest

Last Updated

15 Nov 2018

Look-up Popularity

Time Traveler for infest

The first known use of infest was in 1602

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More Definitions for infest



English Language Learners Definition of infest

of something harmful or unwanted : to be in or over (a place, an animal, etc.) in large numbers


in·​fest | \in-ˈfest \
infested; infesting

Kids Definition of infest

: to spread or swarm in or over in a harmful manner Termites infested the tree.

in·​fest | \in-ˈfest \

Medical Definition of infest 

: to live in or on as a parasite the flea that infests cats horses infested with worms — compare infect

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More from Merriam-Webster on infest

Thesaurus: All synonyms and antonyms for infest

Spanish Central: Translation of infest

Nglish: Translation of infest for Spanish Speakers

Britannica English: Translation of infest for Arabic Speakers

Comments on infest

What made you want to look up infest? Please tell us where you read or heard it (including the quote, if possible).


something that serves to warn or remind

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