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

Producer Greer Simpkin noted that the swarms of flies visible throughout required no visual effects – the location was so badly infested that cast and crew regularly swallowed them during takes. —Naman Ramachandran, Variety, 17 June 2026

The screwworm is actually a fly whose larvae infest the wounds of warm-blooded animals. —Ilena Peng, Fortune, 13 June 2026

To prevent the New World Screwworm from infesting Florida, the state is blocking rescue dogs and cats coming from Texas and New Mexico. —Cbs Miami Team, CBS News, 12 June 2026

The goat was newly confirmed as the latest case to be infested with New World screwworm, Secretary of Agriculture Brooke Rollins said in a press conference Monday. —Julia Jacobo, ABC News, 11 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