What is the meaning of Louse?

Any one of numerous species of small, wingless, suctorial, parasitic insects belonging to a tribe (Pediculina), now usually regarded as degraded Hemiptera. To this group belong of the lice of man and other mammals; as, the head louse of man (Pediculus capitis), the body louse (P. vestimenti), and the crab louse (Phthirius pubis), and many others. See Crab louse, Dog louse, Cattle louse, etc., under Crab, Dog, etc.