lice

UK: /ˈlaɪs/ US: /laɪs/ ,(līs)

From louse (n):

louses

npl (When talking about a person)

lice

npl (All other usages)

WordReference Random House Learner's Dictionary of American English © 2026

lice /laɪs/   n. [plural]

1. Insects a pl. of louse.

WordReference Random House Unabridged Dictionary of American English © 2026

lice  (līs), n. 

1. Insects pl. of louse. 

Collins Concise English Dictionary © HarperCollins Publishers::

lice / laɪs/ noun

1. the plural of louse

WordReference Random House Learner's Dictionary of American English © 2026

louse /n. laʊs; v. also laʊz/   n., pl. lice /laɪs/  for 1–3. lous•es for 4. in Unabridged dictionary, v.,.  loused, lous•ing. 
n. [countable]

1. Insects a small, flat, wingless insect with sucking mouthparts, that lives on humans and animals.
2. Slang Terms a mean, contemptible person.

v. 

3. louse up, [Slang.] to fail to do successfully* botch: [~ + up + object]
   He loused up his opportunity.
   [~ + object + up]
   It's your big chance; don't louse it up.
   [no object]
   He's going to louse up again.

WordReference Random House Unabridged Dictionary of American English © 2026

louse  (n. lous;v. lous, louz), n., pl. lice (līs) for 1–3, lous•es for 4, v., loused, lous•ing. 
n. 

1. Insects 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. Insects any insect of the order Mallophaga (bird louse, biting louse, or chewing louse,) parasitic on birds and mammals, having mouthparts adapted for biting.
3. Insects See plant louse. 
4. Slang Terms a contemptible person, esp. an unethical one.

v.t. 

5. to delouse.
6. louse up, [Slang.] to spoil;
   botch:
   Miscasting loused up the movie.

• bef. 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

Collins Concise English Dictionary © HarperCollins Publishers::

louse / laʊs/ noun (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 humans
   Related adjective(s): pedicular
2. biting louse, 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. (louses) an unpleasant or mean person

verb (transitive)

1. to remove lice from
2. (followed by up) to ruin or spoil

Etymology: Old English lūs; related to Old High German, Old Norse lūs