In mammalogy, one of the long, stiff bristles which grow upon the upper lip and elsewhere upon the head of most mammals; a whisker, as of a cat.In ornithology, a rictal bristle; one of the special set of long, slender, bristle-like or bristly feathers, devoid of vexilla proper, which grow in a series along each side of the rictus or gape of the mouth of many birds, as flycatchers, goatsuckers, and others.In human anatomy, one of the hairs which grow in the nostrils.In entomology, one of the projecting lateral bristles on the upper border of the peristomium or mouth-cavity of certain Diptera.