Bat, n. [Corrupt. from OE. back, backe, balke; cf. Dan. aften-bakke (aften evening), Sw. natt-backa (natt night), Icel. leðr-blaka (leðr leather), Icel. blaka to flutter.] (Zoöl.) One of the Cheiroptera, an order of flying mammals, in which the wings are formed by a membrane stretched between the elongated fingers, legs, and tail. The common bats are small and insectivorous. See Cheiroptera and Vampire.
Silent bats in drowsy clusters cling. Goldsmith.
Bat tick(Zoöl.), a wingless, dipterous insect of the genus Nycteribia, parasitic on bats.