\ˈlau̇s \

Definition of louse 

(Entry 1 of 2)

1 plural lice\ˈlīs \

a : any of various small wingless usually flattened insects (orders Anoplura and Mallophaga) parasitic (see parasite sense 2) 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 \ : a contemptible person : heel what a beast, what a cad, what a louse he had been— Walter Karig


\ˈlau̇s, ˈlau̇z \
loused; lousing

Definition of louse (Entry 2 of 2)

transitive verb

: to remove lice from

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Examples of louse in a Sentence


a problem with head lice Her ex-husband is a real louse.

Recent Examples on the Web: Noun

Each female louse can produce two strings of 1,000 eggs, which means infestations spread quickly within concentrated populations of captive fish. Amanda Little, WIRED, "The Laser Battle Against Blood-Sucking Parasites of the Deep," 23 May 2018 As liquid builds up inside the louse, its internal organs start to shut down from the exhaustion of trying to pump out the water. Karen Weintraub, Scientific American, "Revenge of the Super Lice," 1 June 2017 The ex-husband is uncaring, amoral, self-assured, breezy, confident and a total louse, a convincing case of opposites attracting. Mick Lasalle, Houston Chronicle, "Review: ‘Boundaries’ a trip to nowhere," 3 July 2018 Dangond blends his vallenato with traces of reggaeton and salsa in a track where the man steps in to help the girl get over a louse. Billboard Staff, Billboard, "Viva Friday Playlist: The Best New Latin Music From Bad Bunny, Silvestre Dangond & More," 29 June 2018 Yes, a swarm of stinging sea lice have invaded the shores around Pensacola Beach, leading authorities to post purple flags to warn about the irritating underwater creatures. Matthew Diebel, USA TODAY, "Ee-ew! Authorities warn as sea lice invade beaches in Pensacola, northwest Florida," 27 June 2018 For starters, it's caused by tiny jellyfish larvae, not lice. Amanda Macmillan, Health.com, "What Are Sea Lice, and How Do You Avoid Their Red, Itchy Rash?," 27 June 2018 Once hatched and hooked in with the use of its claws, a louse can live for up to 30 days, feeding on its host's blood. Michael Gordon, charlotteobserver, "Nitpicking or infringement? Companies in patent fight over head lice treatment.," 22 June 2018 Lurking among the captive fish is a tiny nemesis: Lepeophtheirus salmonis, aka the sea louse. Amanda Little, WIRED, "The Laser Battle Against Blood-Sucking Parasites of the Deep," 23 May 2018

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, "Milwaukee fall movie guide: 48 movies, 4 festivals, 11 weeks," 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


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


see louse entry 1

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Dictionary Entries near louse






louse up


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Time Traveler for louse

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

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English Language Learners Definition of louse

: a type of small insect that lives on the bodies of people or animals

: a bad or cruel person


\ˈlau̇s \
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 \
plural lice\ˈlīs \

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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Comments on louse

What made you want to look up louse? Please tell us where you read or heard it (including the quote, if possible).


to reject or criticize sharply

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