n.; pl.Mustaches[ Written also moustache. ] [ F. moustache, It. mostaccio visage, mostacchio mustache, fr. Gr. my`stax upper lip and the beard upon it; cf. ma`stax mouth: cf. Sp. mostacho. ] 1. That part of the beard which grows on the upper lip; hair left growing above the mouth. [ 1913 Webster ]
2. (Zool.) A West African monkey (Cercopithecus cephus). It has yellow whiskers, and a triangular blue mark on the nose. [ 1913 Webster ]
3. (Zool.) Any conspicuous stripe of color on the side of the head, beneath the eye of a bird. [ 1913 Webster ]
4. A stain or discoloration on the upper lip of a person; as, wearing a milk mustache. [ informal ] [ PJC ]