A louse is a tiny insect that lives on the skin of animals and people. If you find a louse in your hair, you'll have to treat your scalp to get rid of any of its friends that might still be lurking there.

Since they tend to travel in groups, the plural form of louse, lice, is much more common than the singular. Lice are small parasites that live on skin cells, blood, or other tiny bits of some host animal. If you're the host animal, you'll probably have an itchy head, and anyone who borrows your pillow or wears your hat will likely get lice too. A louse, informally, is also "an obnoxious person."

Definitions of louse

n wingless usually flattened bloodsucking insect parasitic on warm-blooded animals

sucking louse
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Pediculus humanus, common louse
head or body louse
Pediculus capitis, head louse
infests the head and body of humans
Pediculus corporis, body louse, cootie
a parasitic louse that infests the body of human beings
Phthirius pubis, crab, crab louse, pubic louse
a louse that infests the pubic region of the human body
Type of:
small air-breathing arthropod

n wingless insect with mouth parts adapted for biting; mostly parasitic on birds

bird louse, biting louse
Menopon gallinae, Menopon palladum, chicken louse, shaft louse
a louse parasitic on poultry
Type of:
small air-breathing arthropod

n any of several small insects especially aphids that feed by sucking the juices from plants

plant louse
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any of various small plant-sucking insects
any of various insects that feed and form galls on conifers
Phylloxera vitifoleae, grape louse, grape phylloxera
destructive to various grape plants
jumping plant louse, psylla, psyllid
small active cicada-like insect with hind legs adapted for leaping; feeds on plant juices
oak blight
a black plant louse that lives on oaks and dogwoods
Aphis pomi, apple aphid, green apple aphid
bright green aphid; feeds on and causes curling of apple leaves
Aphis fabae, bean aphid, blackfly
blackish aphid that infests e.g. beans and sugar beets
greenish aphid; pest on garden and crop plants
ant cow
excretes a honeylike substance eaten by ants
woolly aphid, woolly plant louse
secretes a waxy substance like a mass of fine curly white cotton or woolly threads
Adelges piceae, balsam woolly aphid
a variety of adelgid
Adelges abietis, spruce gall aphid
a variety of adelgid
Pineus pinifoliae, pine leaf aphid
a variety of adelgid
woolly adelgid
an insect that feeds on hemlocks; its egg sacs are small fuzzy white balls like artificial snow on a Christmas tree
Type of:
homopteran, homopterous insect
insects having membranous forewings and hind wings

n a person who has a nasty or unethical character undeserving of respect

dirt ball, insect, worm
Type of:
disagreeable person, unpleasant person
a person who is not pleasant or agreeable

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