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[in-fest] /ɪnˈfɛst/
verb (used with object)
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.
to be numerous in, as anything undesirable or troublesome:
the cares that infest the day.
Archaic. to harass.
Origin of infest
late Middle English
1375-1425; late Middle English < Latin infestāre to assail, molest, derivative of infestus hostile
Related forms
infester, noun
reinfest, verb (used with object)
uninfested, adjective
Can be confused
infect, infest, invest. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for infest
Historical Examples
  • It extinguishes every dirty spark of malice and envy, which are but too apt to infest me.

  • 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
  • Others are getting the worms and insects that infest the trees.

    Conservation Reader Harold W. Fairbanks
  • Also, the large maggots with black heads that infest biscuit.

    The Sailor's Word-Book William Henry Smyth
  • You are too green to cope with the sharpers that infest those boats.

    Tom, The Bootblack Horatio Alger
  • A load of miscreants from goodness knows where, who infest me with vermin.

    Tartarin de Tarascon Alphonse Daudet
  • I was struck by the immense number of alligators which infest the river.

    Mark Seaworth William H.G. Kingston
British Dictionary definitions for infest


verb (transitive)
to inhabit or overrun in dangerously or unpleasantly large numbers
(of parasites such as lice) to invade and live on or in (a host)
Derived Forms
infestation, noun
infester, noun
Word Origin
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
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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.

Online Etymology Dictionary, © 2010 Douglas Harper
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infest in Medicine

infest in·fest (ĭn-fěst')
v. in·fest·ed, in·fest·ing, in·fests

  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.

in'fes·ta'tion n.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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