louse

The definition of a louse is a tiny, wingless, sucking parasite.

(noun)

An example of louse is a lice.

See louse in Webster's New World College Dictionary

noun pl. lice

1. any of an order (Anoplura) of small, flat, wingless insects with sucking mouthparts, parasitic on the skin or hair of humans and some other mammals; esp., the human (Pediculus humanus corporis) and (P. h. capitis)
2. any of various arthropods that suck blood or juice from other animals or plants
bird louse
any of various other small insects, arachnids, and crustaceans that are not parasitic, as the book louse or wood louse
Slang a person regarded as mean, contemptible, etc.

Origin: ME lous < OE lus (pl. lys), akin to Ger laus < IE *lūs > Welsh lleuen, Bret laouen

transitive verb loused, lousing

Rare to delouse

See louse in American Heritage Dictionary 4

noun

pl. lice lice (līs) Any of numerous small, flat-bodied, wingless biting or sucking insects of the orders Mallophaga or Anoplura, many of which are external parasites on various animals, including humans.
pl. lous·es (lousˈĭz) Slang A mean or despicable person.