infest

American  

[in-fest] / ɪnˈfɛst /

verb (used with object)

infests, present (3rd person singular) infested, past participle, past infesting present participle

1. to live in or overrun to an unwanted degree or in a troublesome manner, especially as predatory animals or vermin do.

   I had a major problem with cockroaches infesting my kitchen.

   The emerald ash borer has already infested many of the local ash trees.

2. to be numerous in, as anything undesirable or troublesome.

   the cares that infest the day.

3. Archaic. to harass.

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infest British  

/ ɪnˈfɛst /

verb

1. to inhabit or overrun in dangerously or unpleasantly large numbers

2. (of parasites such as lice) to invade and live on or in (a host)

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Other Word Forms

Derived Forms

• infestation
  noun
• infester
  noun
• reinfest
  verb (used with object)

Inflected Forms

Participles

• infesting
  present
• infested
  past

Conjugated Forms

Present

• infest
  simple
• infests
  simple
• have infested
  perfect
• has infested
  perfect
• am infesting
  progressive
• are infesting
  progressive
• is infesting
  progressive
• have been infesting
  perfect progressive
• has been infesting
  perfect progressive

Past

• infested
  simple
• had infested
  perfect
• was infesting
  progressive
• were infesting
  progressive
• had been infesting
  perfect progressive

Future

• will infest
  simple
• will have infested
  perfect
• will be infesting
  progressive
• will have been infesting
  perfect progressive

Etymology

Origin of infest

First recorded in 1375–1425; from late Middle English, from Latin infestāre “to assail, molest,” from infestus “hostile”

Explanation

The verb infest means to invade in large number, often resisting control and causing damage or hardship. Bedbugs can infest people's belongings and even their bodies, or mice may infest your kitchen if you leave the cheese out too often. Infest comes from Latin: in- means "not" and festus means "able to be seized." So infest describes something is not able to be seized, typically because it's present in such large numbers. For example, mosquitoes may infest your backyard during the summer and annoy you when you're trying to relax. Infest is usually used to describe pests, such as bugs or rodents, that overrun something in such large number that they are difficult to control.

Example Sentences

See Examples For:

infest infests infested infesting

Officials added that the calf was undergoing treatment and improving, and emphasized that the worms do not infest food sources like meat, fruit or vegetables.

From Barron's ● Jun. 4, 2026

When Banksy’s first examples from this series were unveiled in London in 2005, the show caused a stir because he also arranged for around 200 live rats to infest the gallery.

From The Wall Street Journal ● May 21, 2026

A more accurate metaphor would be credit termites — insects that infest and destroy structural timbers.

From MarketWatch ● May 20, 2026

A parasitic fly whose maggots can infest living livestock, birds, pets and humans, could threaten California soon.

From Los Angeles Times ● Sep. 17, 2025

With insects that infest crops the story is the same.

From "Silent Spring" by Rachel Carson

The pollution that infests those systems can include everything from silt and natural debris to asbestos, heavy metals, radioactive isotopes and other harmful contaminants released when man-made structures burn.

From New York Times ● Sep. 26, 2022

English ivy infests millions of trees across the country, killing them by choking, stealing nutrients and adding weight that can be deadly in high winds.

From Washington Post ● Apr. 29, 2022

Here’s the key: During a séance, the vampires are confronted by their dead spirits; one infests a doll.

From Los Angeles Times ● Aug. 24, 2020

But because asbestos infests the plaster and tiles at 6th and Baldridge, initial estimates for that job are $35,000, according to North Braddock officials.

From Washington Times ● Oct. 13, 2018

This insect infests about a third of Africa, posing a menace to human health and preventing the keeping of livestock in an area of some 4% million square miles of wooded grasslands.

From "Silent Spring" by Rachel Carson

The Mexican fruit fly enters California when travelers bring fruits or vegetables back from regions that are infested, according to the department.

From Los Angeles Times ● Jun. 30, 2026

Michael Schmoyer -- the associate administrator for the country's Animal and Plant Health Inspection Service and head of the NWS Directorate -- said the infested beef calf "is not a danger to the food supply."

From Barron's ● Jun. 4, 2026

“Our business is infested with idiots,” he famously warned, “who try to impress by using pretentious jargon.”

From The Wall Street Journal ● Apr. 30, 2026

It was infested with rats and cockroaches, and smelt "nauseating".

From BBC ● Mar. 4, 2026

His hair was tangled into greasy locks, infested by nits.

From "The Many Assassinations of Samir, the Seller of Dreams" by Daniel Nayeri

Plus, the $313 million injury bug infesting the NBA playoffs, Ted Turner’s day managing the Braves and Jason Gay.

From The Wall Street Journal ● May 15, 2026

Solanum elaeagnifolium -- also known as silverleaf nightshade -- can be found from south Texas to South Africa and Greece, infesting fields and soaking up valuable nutrients intended for cash crops.

From Science Daily ● Jun. 3, 2024

The wingless, pill-shaped insects feed on mammalian blood and, as indicated by their name, are notorious for infesting human dwellings.

From Salon ● Mar. 13, 2024

It comes after widespread panic of bedbugs infesting London after a widely reported outbreak in Paris.

From BBC ● Nov. 1, 2023

They just pushed themselves along the ground with their hands and arms, but that only led to tuktuk infesting their hands.

From "Lost Boy, Lost Girl" by John Bul Dau