hair (hairs plural )
1 n-var Your hair is the fine threads that grow in a mass on your head.
I wash my hair every night...
2 n-var Hair is the short, fine threads that grow on different parts of your body.
The majority of men have hair on their chest...
3 n-var Hair is the threads that cover the body of an animal such as a dog, or make up a horse's mane and tail.
I am allergic to cat hair.
4 If you let your hair down, you relax completely and enjoy yourself.
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let one's hair down phrase
...the world-famous Oktoberfest, a time when everyone in Munich really lets their hair down.
5 Something that makes your hair stand on end shocks or frightens you very much.
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make sb's hair stand on end phrase
This was the kind of smile that made your hair stand on end.
6 If you say that someone has not a hair out of place, you are emphasizing that they are extremely smart and neatly dressed.
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not a hair out of place phrase
(emphasis)
She had a lot of make-up on and not a hair out of place.
7 If you say that someone faced with a shock or a problem does not turn a hair, you mean that they do not show any surprise or fear, and remain completely calm.
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not turn a hair phrase
No one seems to turn a hair at the thought of the divorced Princess marrying.
8 If you say that someone is splitting hairs, you mean that they are making unnecessary distinctions between things when the differences between them are so small they are not important.
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split hairs phrase
Don't split hairs. You know what I'm getting at.