Sleeper \Sleep"er\, n. 1. One who sleeps; a slumberer; hence, a drone, or lazy person. 2. That which lies dormant, as a law. [Obs.] --Bacon. 3. A sleeping car. [Colloq. U.S.] 4. (Zo["o]l.) An animal that hibernates, as the bear. 5. (Zo["o]l.) (a) A large fresh-water gobioid fish ({Eleotris dormatrix}). (b) A nurse shark. See under {Nurse}.