\ ˈlau̇s How to pronounce louse (audio) \

Definition of louse

 (Entry 1 of 2)

1 plural lice\ ˈlīs How to pronounce louse (audio) \
a : any of various small wingless usually flattened insects (orders Anoplura and Mallophaga) parasitic on warm-blooded animals
b : a small usually sluggish arthropod (such as a biting louse) that lives on other animals or on plants and sucks their blood or juices
c : any of several small arthropods (such as a book louse) that are not parasitic
2 plural louses\ ˈlau̇-​səz How to pronounce louse (audio) \ : a contemptible person : heel what a beast, what a cad, what a louse he had been— Walter Karig


\ ˈlau̇s How to pronounce louse (audio) , ˈlau̇z How to pronounce louse (audio) \
loused; lousing

Definition of louse (Entry 2 of 2)

transitive verb

: to remove lice from

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Synonyms for louse

Synonyms: Noun

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Examples of louse in a Sentence

Noun a problem with head lice Her ex-husband is a real louse.
Recent Examples on the Web: Noun The fatal grape louse phylloxera was slowly overtaking the plants. Esther Mobley, San Francisco Chronicle, 12 June 2021 Here, too, are a warmth and a curiosity for even the most minor of characters (except that louse of a boyfriend) and a faith in the lessons that a pliant, earnest — and, honestly, not terribly interesting — young person might accrue over time. Globe Staff, BostonGlobe.com, 4 Mar. 2021 An adult louse can be light brown or grey, is two-three millimeters long, and has a lifespan of about 30 days. Kaitlyn Pirie, Good Housekeeping, 27 Aug. 2020 But unlike other, more popular rootstocks, St. George later turned out to be resistant to phylloxera, the grapevine louse that wiped out much of California’s wine grape acreage in a 1980s epidemic. Esther Mobley, SFChronicle.com, 10 Nov. 2020 The starvation made fighting any disease that did emerge near impossible, and louse vectors spread easily due to a lack of adequate sanitation and an abundance of hosts. Courtney Sexton, Smithsonian Magazine, 27 July 2020 Virtually all vines of that era were killed by phylloxera, a grape louse that spread in the 1980s, but Volker Eisele’s were among the rare plants that had been grafted onto phylloxera-resistant St. George rootstock. Esther Mobley, SFChronicle.com, 4 Sep. 2020 Running a fine tooth louse comb through natural Black hair without protecting the hair itself can cause a lot of frustrating breakage. Kaitlyn Pirie, Good Housekeeping, 27 Aug. 2020 The poor fish’s tongue withers into a useless nub, leaving the mouth vacant for the louse itself to physically take its place, helping its host move food around its mouth and grind big morsels down to size. Katherine J. Wu, Smithsonian Magazine, 14 Feb. 2020 Recent Examples on the Web: Verb Will Ferrell figure out a way to get along, their fathers (Mel Gibson, John Lithgow) show up for the holidays to louse everything up in this comedy sequel. Chris Foran, Milwaukee Journal Sentinel, 31 Aug. 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'louse.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of louse


before the 12th century, in the meaning defined at sense 1a


14th century, in the meaning defined above

History and Etymology for louse

Noun and Verb

Middle English lous, from Old English lūs; akin to Old High German lūs louse, Welsh llau lice

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Time Traveler for louse

Time Traveler

The first known use of louse was before the 12th century

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Statistics for louse

Last Updated

18 Jun 2021

Cite this Entry

“Louse.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/louse. Accessed 20 Jun. 2021.

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More Definitions for louse



English Language Learners Definition of louse

: a type of small insect that lives on the bodies of people or animals
informal : a bad or cruel person


\ ˈlau̇s How to pronounce louse (audio) \
plural lice\ ˈlīs \

Kids Definition of louse

1 : a small, wingless, and usually flat insect that lives on the bodies of warm-blooded animals
2 : an insect or related arthropod that resembles a body louse and feeds on plant juices or decaying matter


\ ˈlau̇s How to pronounce louse (audio) \
plural lice\ ˈlīs How to pronounce louse (audio) \

Medical Definition of louse

: any of the small wingless usually flattened insects that are parasitic on warm-blooded animals and constitute the orders Anoplura and Mallophaga


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