any of the numerous fine, usually cylindrical, keratinous filaments growing from the skin of humans and animals; a pilus.

an aggregate of such filaments, as that covering the human head or forming the coat of most mammals.

a similar fine, filamentous outgrowth from the body of insects, spiders, etc.

Botany . a filamentous outgrowth of the epidermis.

cloth made of hair from animals, as camel and alpaca.

a very small amount, degree, measure, magnitude, etc.; a fraction, as of time or space

He lost the race by a hair.

get in someone's hair

Slang . to annoy or bother someone

Their snobbishness gets in my hair.

hair of the dog, Informal . a drink of liquor

supposed to relieve a hangover

Even a hair of the dog didn't help his aching head. Also, hair of the dog that bit one.

let one's hair down

Informal .

to relax; behave informally

He finally let his hair down and actually cracked a joke.

to speak candidly or frankly; remove or reduce restraints

He let his hair down and told them about his anxieties.

make one's hair stand on end

to strike or fill with horror; terrify

The tales of the jungle made our hair stand on end.

split hairs

to make unnecessarily fine or petty distinctions: To argue about whether they arrived at two o'clock or at 2

01 is just splitting hairs.

tear one's hair, to manifest extreme anxiety, grief

or anger

He's tearing his hair over the way he was treated by them. Also, tear one's hair out.

to a hair

perfect to the smallest detail; exactly

The reproduction matched the original to a hair.

without turning a hair, without showing the least excitement or emotion. Also

not turn a hair.

noun

beard , bristle , cilium , coiffure , cowlick , cut , down , eyebrow , eyelash , feeler , fiber , filament , fluff , fringe , frizzies , fur , grass , haircut , hairstyle , lock , mane , mop * , moustache , quill , ruff , shock , sideburn , split ends , strand , thatch , tress , tuft , vibrissa , villus , whiskers , wig , woolnotes:hair is any of the cylindrical filaments characteristically growing from the epidermis of a mammal; a hare is a large , long-eared and long-legged rabbit; an heir is a person who is entitled by law or by the terms of a will to inherit the estate of another , breath , dash , ghost , hint , intimation , semblance , shadow , soupon , streak , suggestion , suspicion , taste , tinge , touch , trace , whiff , whisper , byssus , chevelure , chignon , cilia , coif , crinosity , escutcheon , feather , forelock , frill , hirsutism , palpus , pelage , pilosis , pilosism , pilosity , pilus , pubes , pubescence , ringlet , shag , tentaculum , tresses , trichosis