n. The beard worn on the upper lip of men; the unshaven hair of the upper lip: frequently used in the plural, as if the hair on each side of the lip were to be regarded as a mustache.n. . A long ringlet hanging beside the face, a part of a woman's head-dress in the seventeenth century.n. In zoology:n. Hairs or bristles like a mustache; whiskers; rictal vibrissæ mystaces.n. A mystacine, malar, or maxillary stripe of color in a bird's plumage.