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See more synonyms for infest on Thesaurus.com
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: Sharks infested the coastline.
  2. to be numerous in, as anything undesirable or troublesome: the cares that infest the day.
  3. Archaic. to harass.
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Origin of infest

1375–1425; late Middle English < Latin infestāre to assail, molest, derivative of infestus hostile
Related formsin·fest·er, nounre·in·fest, verb (used with object)un·in·fest·ed, adjective
Can be confusedinfect infest invest
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for infest

pollute, defile, overwhelm, beset, assail, flock, worry, fill, crowd, pester, ravage, swarm, invade, teem, infect, plague, abound, press, penetrate, crawl

Examples from the Web for infest

Historical Examples of infest

  • It extinguishes every dirty spark of malice and envy, which are but too apt to infest me.

    The Letters of Robert Burns

    Robert Burns

  • Insects do not seem to infest it as they do the ostreatus and the sapidus.

  • They infest desert places, and are nocturnal in their habits.

    History of Religion

    Allan Menzies

  • From them have come the many species of shark that now infest our ocean.

    Unwritten Literature of Hawaii

    Nathaniel Bright Emerson

  • Other species eat most of the scales which infest fruit and forest trees.

    Checking the Waste

    Mary Huston Gregory

British Dictionary definitions for infest


verb (tr)
  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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Derived Formsinfestation, nouninfester, noun

Word Origin for infest

C15: from Latin infestāre to molest, from infestus hostile
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for infest


late 15c., "to attack, assail, hurt, distress, annoy," from Middle French infester, from Latin infestare "to attack, disturb, trouble," from infestus "hostile, dangerous," originally "inexorable, not able to be handled," from in- "not, opposite of" (see in- (1)) + -festus "(able to be) seized." Sense of "swarm over in large numbers" first recorded c.1600. Related: Infested; infesting.

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Online Etymology Dictionary, © 2010 Douglas Harper

infest in Medicine


  1. To live as a parasite in or on tissues or organs or on the skin and its appendages.
  2. To inhabit or overrun in numbers large enough to be harmful, threatening, or obnoxious.
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Related formsin′fes•tation n.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.