infest

American  

[in-fest] / ɪnˈfɛst /

verb (used with object)

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

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

Etymology

Origin of infest

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

Example Sentences

"NWS can infest livestock, pets, wildlife, occasionally birds, and in rare cases, people."

From BBC • Aug. 25, 2025

But it's not technically possible for them to infest their own home.

From Salon • Jul. 21, 2024

It’s not all that uncommon for maggots to infest and grow in poorly healing human tissue—it’s called myiasis.

From Slate • Feb. 25, 2024

When mites infest a colony, they inflict damage both by living and feeding on bees directly and also by spreading DWV.

From Science Daily • Nov. 14, 2023

Skilled at creeping under floorboards and behind skirting boards, they infest houses.

From "Fantastic Beasts and Where to Find Them" by J.K. Rowling