infest

verb

in·​fest in-ˈfest 

infested; infesting; infests

transitive verb

1

: to spread or swarm in or over in a troublesome manner

shark-infested waters

2

: to live in or on as a parasite

infestant

in-ˈfe-stənt 

noun

infestation

ˌin-ˌfe-ˈstā-shən 

noun

infester

in-ˈfe-stər 

noun

Synonyms of infest

• plague
• infect
• overrun
• crawl
• overwhelm

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 flies lay their eggs in open wounds of animals like cattle, but wildlife, pets and occasionally even humans can be infested. —Jeffrey Collins, Fortune, 9 June 2026

While these cases highlight the risks of wounds and vulnerabilities, many others show that the flies will happily infest in normal orifices, such as the ears and nose. —Beth Mole, ArsTechnica, 9 June 2026

Females lay their eggs in open wounds of any warm-blooded animal such as cattle, but wildlife, pets and occasionally even humans can be infested. —ABC News, 8 June 2026

Any warm-blooded animal, including wildlife, pets and occasionally even humans, can be infested. —CBS News, 8 June 2026

Word History

Etymology

French infester, from Latin infestare, from infestus hostile

First Known Use

1602, in the meaning defined at sense 1

Rhymes for infest

• abreast
• accessed
• addressed
• appressed
• armrest
• arrest
• assessed
• attest
• backrest
• behest
• bequest
• caressed

Kids Definition

infest

verb

in·​fest in-ˈfest 

1

: to spread or swarm in or over in a troublesome manner

a neighborhood infested with crime

shark-infested waters

2

: to live in or on as a parasite

horses infested with worms

infestation

ˌin-ˌfes-ˈtā-shən 

noun

Medical Definition

infest

transitive verb

in·​fest in-ˈfest 

: to live in or on as a parasite

the flea that infests cats

horses infested with worms

compare infect