[noun lous; verb lous, louz]
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noun, plural lice [lahys] /laɪs/ for 1–3, lous·es for 4.
  1. any small, wingless insect of the order Anoplura (sucking louse), parasitic on humans and other mammals and having mouthparts adapted for sucking, as Pediculus humanus (body louse or head louse) and Phthirius pubis (crab louse or pubic louse).
  2. any insect of the order Mallophaga (bird louse, biting louse, or chewing louse), parasitic on birds and mammals, having mouthparts adapted for biting.
  3. plant louse.
  4. Slang. a contemptible person, especially an unethical one.
verb (used with object), loused, lous·ing.
  1. to delouse.
Verb Phrases
  1. louse up, Slang. to spoil; botch: Miscasting loused up the movie.

Origin of louse

before 900; 1910–15 for def 4; Middle English lous(e), luse, plural lise, lice; Old English lūs, plural lȳs; cognate with Dutch luis, German Laus, Old Norse lūs
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for louse

rat, scoundrel, knave, cad, cootie

Examples from the Web for louse

Contemporary Examples of louse

Historical Examples of louse

  • Said the other: "I will become a louse, so as to be able to stay always in her bosom."

    Aino Folk-Tales

    Basil Hall Chamberlain

  • The man might be a louse, but he was also a fighting machine of first order, still.

    Police Your Planet

    Lester del Rey

  • Dont claw your back as if after a flea; or your head, as if after a louse.

  • There's always stuff in the way to louse up a good flight plan.

    Eight Keys to Eden

    Mark Irvin Clifton

  • The man has not the soul of a louse, and as for her, she's the finest gold!

    Doom Castle

    Neil Munro

British Dictionary definitions for louse


noun plural lice (laɪs)
  1. any wingless bloodsucking insect of the order Anoplura: includes Pediculus capitis (head louse), Pediculus corporis (body louse), and the crab louse, all of which infest manRelated adjective: pedicular
  2. biting louse or bird louse any wingless insect of the order Mallophaga, such as the chicken louse: external parasites of birds and mammals with biting mouthparts
  3. any of various similar but unrelated insects, such as the plant louse and book louse
  4. plural louses slang an unpleasant or mean person
verb (tr)
  1. to remove lice from
  2. (foll by up) slang to ruin or spoil

Word Origin for louse

Old English lūs; related to Old High German, Old Norse lūs
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 louse

"parasitic insect infecting human hair and skin," Old English lus, from Proto-Germanic *lus (cf. Old Norse lus, Middle Dutch luus, Dutch luis, Old High German lus, German Laus), from PIE *lus- "louse" (cf. Welsh lleuen "louse"). Slang meaning "obnoxious person" is from 1630s. The plural lice (Old English lys) shows effects of i-mutation. The verb meaning "to clear of lice" is from late 14c.; to louse up "ruin, botch" first attested 1934, from the literal sense (of bedding), from 1931.

Online Etymology Dictionary, © 2010 Douglas Harper

louse in Medicine


n. pl. lice (līs)
  1. Any of numerous small, flat-bodied, wingless biting or sucking insects of the orders Mallophaga or Anoplura, many of which are external parasites on humans.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.