1.  The collection or mass of filaments growing from the skin of an animal, and forming a covering for a part of the head or for any part or the whole of the body. [1913 Webster]

2.  One the above-mentioned filaments, consisting, in vertebrate animals, of a long, tubular part which is free and flexible, and a bulbous root imbedded in the skin. [1913 Webster]
"Then read he me how Sampson lost his hairs." [1913 Webster]
"And draweth new delights with hoary hairs." [1913 Webster]

3.  Hair (human or animal) used for various purposes; as, hair for stuffing cushions. [1913 Webster]

4.  A slender outgrowth from the chitinous cuticle of insects, spiders, crustaceans, and other invertebrates. Such hairs are totally unlike those of vertebrates in structure, composition, and mode of growth. [1913 Webster]

5.  An outgrowth of the epidermis, consisting of one or of several cells, whether pointed, hooked, knobbed, or stellated. Internal hairs occur in the flower stalk of the yellow frog lily (Nuphar). [1913 Webster]

6.  A spring device used in a hair-trigger firearm. [1913 Webster]

7.  A haircloth. Chaucer. [1913 Webster]

8.  Any very small distance, or degree; a hairbreadth. [1913 Webster]
" Hairs is often used adjectively or in combination; as, hairbrush or hair brush, hair dye, hair oil, hairpin, hair powder, a brush, a dye, etc., for the hair." [1913 Webster]

hair, n.
1 a any of the fine threadlike strands growing from the skin of mammals, esp. from the human head. b these collectively (his hair is falling out).
2 a an artificially produced hairlike strand, e.g. in a brush. b a mass of such hairs.
3 anything resembling a hair.
4 an elongated cell growing from the epidermis of a plant.
5 a very small quantity or extent (also attrib.: a hair crack).

Idiom:
get in a person's hair colloq. encumber or annoy a person. hair-drier (or -dryer) an electrical device for drying the hair by blowing warm air over it. hair-grass any of various grasses, esp. of the genus Deschampsia, Corynephous, Aira, etc., with slender stems. hair of the dog see DOG. hair-raising extremely alarming; terrifying. hair's breadth a very small amount or margin. hair shirt a shirt of haircloth, worn formerly by penitents and ascetics. hair-shirt adj. (attrib.) austere, harsh, self-sacrificing. hair-slide Brit. a (usu. ornamental) clip for keeping the hair in position. hair-splitter a quibbler. hair-splitting adj. & n. making overfine distinctions; quibbling. hair-trigger a trigger of a firearm set for release at the slightest pressure. keep one's hair on Brit. colloq. remain calm; not get angry. let one's hair down colloq. abandon restraint; behave freely or wildly. make one's hair stand on end alarm or horrify one. not turn a hair remain apparently unmoved or unaffected.

Derivative:
haired adj. (also in comb.). hairless adj. hairlike adj.

Etymology:
OE h{aelig}r f. Gmc

N  smallness, littleness, tenuity, paucity, fewness, meanness, insignificance (unimportance), mediocrity, moderation, small quantity, modicum, trace, hint, minimum, vanishing point, material point, atom, particle, molecule, corpuscle, point, speck, dot, mote, jot, iota, ace, minutiae, details, look, thought, idea, soupcon, dab, dight, whit, tittle, shade, shadow, spark, scintilla, gleam, touch, cast, grain, scruple, granule, globule, minim, sup, sip, sop, spice, drop, droplet, sprinkling, dash, morceau, screed, smack, tinge, tincture, inch, patch, scantling, tatter, cantlet, flitter, gobbet, mite, bit, morsel, crumb, seed, fritter, shive, snip, snippet, snick, snack, snatch, slip, scrag, chip, chipping, shiver, sliver, driblet, clipping, paring, shaving, hair, nutshell, thimbleful, spoonful, handful, capful, mouthful, fragment, fraction, drop in the ocean, animalcule, trifle, mere nothing, next to nothing, hardly anything, just enough to swear by, the shadow of a shade, finiteness, finite quantity, small, little, diminutive, minute, fine, inconsiderable, paltry, faint, slender, light, slight, scanty, scant, limited, meager, sparing, few, low, so-so, middling, tolerable, no great shakes, below par, under par, below the mark, at a low ebb, halfway, moderate, modest, tender, subtle, inappreciable, evanescent, infinitesimal, homeopathic, very small, atomic, corpuscular, microscopic, molecular, subatomic, mere, simple, sheer, stark, bare, near run, dull, petty, shallow, stolid, ungifted, unintelligent, to a small extent, on a small scale, a little bit, a wee bit, slightly, imperceptibly, miserably, wretchedly, insufficiently, imperfectly, faintly, passably, pretty well, well enough, partially, in part, in a certain degree, to a certain degree, to a certain extent, comparatively, some, rather in some degree, in some measure, something, somewhat, simply, only, purely, merely, at least, at the least, at most, at the most, ever so little, as little as may be, tant soit peu, in ever so small a degree, thus far, pro tanto, within bounds, in a manner, after a fashion, so to speak, almost, nearly, well-nigh, short of, not quite, all but, near upon, close upon, peu s'en faut, near the mark, within an ace of, within an inch of, on the brink of, scarcely, hardly, barely, only just, no more than, about, thereabouts, somewhere about, nearly, say, be the same, be little more or less, no ways, no way, no wise, not at all, not in the least, not a bit, not a bit of it, not a whit, not a jot, not a shadow, in no wise, in no respect, by no means, by no manner of means, on no account, at no hand, dare pondus idonea fumo, magno conatu magnas nugas, small sands the mountain, moments make the year.

N  filament, line, fiber, fibril, funicle, vein, hair, capillament, cilium, cilia, pilus, pili, tendril, gossamer, hair stroke, veinlet, venula, venule, wire, string, thread, packthread, cotton, sewing silk, twine, twist, whipcord, tape, ribbon, cord, rope, yarn, hemp, oakum, jute, strip, shred, slip, spill, list, band, fillet, fascia, ribbon, riband, roll, lath, splinter, shiver, shaving, beard, ramification, strand, filamentous, filamentiferous, filaceous, filiform, fibrous, fibrillous, thread-like, wiry, stringy, ropy, capillary, capilliform, funicular, wire-drawn, anguilliform, flagelliform, hairy, taeniate, taeniform, taenioid, venose, venous.

N  roughness, tooth, grain, texture, ripple, asperity, rugosity, salebrosity, corrugation, nodosity, arborescence, pilosity, brush, hair, beard, shag, mane, whisker, moustache, imperial, tress, lock, curl, ringlet, fimbriae, pili, cilia, villi, lovelock, beaucatcher, curl paper, goatee, papillote, scalp lock, plumage, plumosity, plume, panache, crest, feather, tuft, fringe, toupee, wool, velvet, plush, nap, pile, floss, fur, down, byssus, moss, bur, fluff, knot (convolution), rough, uneven, scabrous, scaly, knotted, rugged, rugose, rugous, knurly, asperous, crisp, salebrous, gnarled, unpolished, unsmooth, roughhewn, craggy, cragged, crankling, scraggy, prickly, arborescent, leafy, well-wooded, feathery, plumose, plumigerous, laciniate, laciniform, laciniose, pappose, pileous, pilose, trichogenous, trichoid, tufted, fimbriated, hairy, ciliated, filamentous, hirsute, crinose, crinite, bushy, hispid, villous, pappous, bearded, pilous, shaggy, shagged, fringed, befringed, setous, setose, setaceous, like quills upon the fretful porcupine, rough as a nutmeg grater, rough as a bear, downy, velvety, flocculent, woolly, lanate, lanated, lanuginous, lanuginose, tomentose, fluffy, against the grain, cabello luengo y corto el seso.

berenice's hair, body hair, camel's hair, cross hair, crotch hair, false hair, guard hair, hair ball, hair care, hair cell, hair coloring, hair curler, hair drier, hair dryer, hair dye, hair follicle, hair gel, hair grass, hair grease, hair mousse, hair of the dog, hair oil, hair seal, hair shirt, hair slide, hair space, hair spray, hair stroke, hair style, hair tonic, hair trigger, hair worm, hand by a hair, head of hair, ingrown hair, lady's hair, maid's hair, pele's hair, pubic hair, root hair, sable's hair pencil, sensory hair, stinging hair