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.

---

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)

---

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

An infestation occurs when fly maggots infest the living flesh of warm-blooded animals, the CDC says.

From Los Angeles Times • Sep. 17, 2025

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

From Salon • Jul. 21, 2024

A parasitic worm that can infest the brains of moose appears to be playing a role in the decline of the iconic animal in some regions of North America.

From Science Daily • May 15, 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

“She might. I wouldn’t mind knowing where the lifeboat is. Besides, it didn’t take Beatrice long to infest Mrs. Cranston’s fur cape. What will she get up to next, do you suppose?”

From "Secrets at Sea" by Richard Peck