1any of the fine thread-like strands growing from the skin of humans, mammals, and some other animals:coarse outer hairs overlie the thick underfurthick black hairs on his huge arms
a fine thread-like strand growing from the epidermis of a plant, or forming part of a living cell:scalloped leaves edged with silver hairsit damages the cilia, tiny hairs that clear invading bacteria from the lung
2 [mass noun] hairs collectively, especially those growing on a person’s head:her shoulder-length fair hair
3 (a hair) a very small quantity or extent:his magic takes him a hair above the competition
hair of the dog
informal an alcoholic drink taken to cure a hangover.
[from hair of the dog that bit you, formerly recommended as an efficacious remedy for the bite of a mad dog]
a hair's breadth
a very small amount or margin:you escaped death by a hair’s breadth
in (or out of) someone's hair
informal annoying (or ceasing to annoy) someone:they sent him to America, just to get him out of their hair
keep your hair on!
British informal used to urge someone not to panic or lose their temper.
let one's hair down
informal behave uninhibitedly:let your hair down and just have some fun
make someone's hair stand on end
alarm or horrify someone:any kind of siren makes my hair stand on end
not turn a hair
remain apparently unmoved or unaffected:if I was told I’d been sacked tomorrow, I don’t think I’d turn a hair
make small and overfine distinctions:one of those medieval disputes which split hairs endlessly
[in combination]:a curly-haired boy
Old Englishhǣr, of Germanic origin; related to Dutch haar and German Haar