‖n. pl. [ NL., fr. Gr. mo`nos single + &unr_; hole. ] (Zool.) A subclass of Mammalia, having a cloaca in which the ducts of the urinary, genital, and alimentary systems terminate, as in birds. The female lays eggs like a bird. See Duck mole, under Duck, and Echidna. [ 1913 Webster ]