- 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 humanus(body louse ) or Pediculus humanus capitis(head louse ) and Phthirius pubis(crab louse, or pubic louse ).
- any insect of the order Mallophaga (bird louse, biting louse, or chewing louse ), parasitic on birds and mammals, having mouthparts adapted for biting.
- plant louse.
- a contemptible person, especially an unethical one.
- to delouse.
- to spoil; botch: Miscasting loused up the movie.
- 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 man
- any wingless insect of the order Mallophaga, such as the chicken louse: external parasites of birds and mammals with biting mouthparts
- any of various similar but unrelated insects, such as the plant louse and book louse
- an unpleasant or mean person
- to remove lice from
- to ruin or spoil
