in·​fest | \ in-ˈfest How to pronounce infest (audio) \
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

Keep scrolling for more

Other Words from infest

infestant \ in-​ˈfe-​stənt How to pronounce infestant (audio) \ noun
infestation \ ˌin-​ˌfe-​ˈstā-​shən How to pronounce infestation (audio) \ noun
infester \ in-​ˈfe-​stər How to pronounce infester (audio) \ noun

Synonyms for infest



Visit the Thesaurus for More 

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 current outbreak likely began when people drew water from a bat-infested well, according to the India’s National Centre for Disease Control, which is leading the investigation. Emily Baumgaertner, New York Times, "Nipah Virus, Dangerous and Little Known, Spreads in India," 4 June 2018 Flights from New Jersey 'infested' with bed bugs, passengers claim. Fox News, "FOX NEWS FIRST: Mass shooting stuns Toronto, too early to determine if it's terror; Trump warns Iran," 23 July 2018 Behind that sanguine view is the fact that speculative mortgages no longer infest the housing market, one common culprit in financial meltdowns, and banks, another culprit, have plenty of loss-absorbing capital and liquidity. Greg Ip, WSJ, "How Long Can the Great Jobs Picture Continue? The Fed Thinks Indefinitely," 2 Nov. 2018 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

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.

See More

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

Keep scrolling for more

Learn More about infest

Statistics for infest

Last Updated

8 Feb 2019

Look-up Popularity

Time Traveler for infest

The first known use of infest was in 1602

See more words from the same year

Keep scrolling for more

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 How to pronounce infest (audio) \
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 How to pronounce infest (audio) \

Medical Definition of infest

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

Keep scrolling for more

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).


to corrupt or become corrupted

Get Word of the Day daily email!

Test Your Vocabulary

A Green Quiz

  • shamrock
  • What is the best definition of green-eyed monster?
Spell It

Can you spell these 10 commonly misspelled words?

Bee Cubed

Test Your Knowledge - and learn some interesting things along the way.


Love words? Need even more definitions?

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