vibrissa

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of the long stiff hairs that project from the snout or brow of most mammals, as the whiskers of a cat.
2. n. One of several long modified feathers that grow along the gape of the mouth of insect-eating birds.

Century Dictionary and Cyclopedia

1. 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. They are tactile organs, or feelers, and are sometimes called tactile hairs (pili tactiles). There is a popular notion that the whiskers reach out just far enough on each side to enable the animal to judge whether a hole or other close passage is large enough for it to pass through, and very probably this is true in many cases. See cuts under mouse, ocelot, panther, serval, tiger, and tiger-cat.
2. 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. When very long, as in the goatsucker, they are sometimes called vibrissæ pectinatæ, and may have lateral filaments, as in the chuck-will'swidow. The use of the vibrissæ is supposed to be to entangle the legs and wings of insects, and thus diminish or prevent their struggling when caught, as the bristles are observed to be specially well developed in insectivorous birds which take their prey on the wing. See cuts under Platyrhynehus, flycatcher, goatsucker, and whippoorwill.
3. In human anatomy, one of the hairs which grow in the nostrils.
4. In entomology, one of the projecting lateral bristles on the upper border of the peristomium or mouth-cavity of certain Diptera.

Wiktionary

1. n. Any of the tactile whiskers on the nose of an animal such as a cat
2. n. Any similar feather near the mouth of some birds

GNU Webster's 1913

1. n. (Anat.) One of the specialized or tactile hairs which grow about the nostrils, or on other parts of the face, in many animals, as the so-called whiskers of the cat, and the hairs of the nostrils of man.
2. n. (Zoöl.) The bristlelike feathers near the mouth of many birds.

WordNet 3.0

1. n. a long stiff hair growing from the snout or brow of most mammals as e.g. a cat