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

Because food can be scarce there and people fear theft, individuals will store rice in their dirt-floor homes, Wagner says, allowing close contact with the rats that infest the island. — Faye Flam, Scientific American, 27 Oct. 2026

These parasites primarily infest the eyes of cats and dogs but can sometimes make their way into human eyes inadvertently. — Beth Mole, ArsTechnica, 26 Oct. 2026

The physical conditions are so bad that cells are infested with mold and vermin, the letter said. — Jessica Ryan, AJC.com, 19 Oct. 2026

Students have drawn attention to rundown classrooms that lack basics such as desks and chairs, become sweltering in summer without air conditioning and, in some cases, are infested with rats. — ABC News, 6 Oct. 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