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). 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. haired adj. (also in comb.). hairless adj. hairlike adj.
[ OE hr f. Gmc ]