hair

American  

[hair] / hɛər /

noun

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

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

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

4. Botany. a filamentous outgrowth of the epidermis.

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

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

   He lost the race by a hair.

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idioms

1. tear one's hair, to manifest extreme anxiety, grief, or anger: Also tear one's hair out.

   He's tearing his hair over the way he was treated by them.

2. 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.

3. 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.

4. without turning a hair, without showing the least excitement or emotion. Also not turn a hair.

5. to a hair, perfect to the smallest detail; exactly.

   The reproduction matched the original to a hair.

6. hair of the dog, a drink of liquor, supposed to relieve a hangover: Also hair of the dog that bit one.

   Even a hair of the dog didn't help his aching head.

7. let one's hair down,

   1. to relax; behave informally.

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

   2. to speak candidly or frankly; remove or reduce restraints.

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

8. get in someone's hair, to annoy or bother someone.

   Their snobbishness gets in my hair.

hair British  

/ hɛə /

noun

1. any of the threadlike pigmented structures that grow from follicles beneath the skin of mammals and consist of layers of dead keratinized cells

2. a growth of such structures, as on the human head or animal body, which helps prevent heat loss from the body

3. botany any threadlike outgrowth from the epidermis, such as a root hair

4. 1. a fabric or material made from the hair of some animals

   2. ( as modifier )

      a hair carpet

      a hair shirt

5. another word for hair's-breadth

   to lose by a hair

6. informal to annoy someone persistently

7. an alcoholic drink taken as an antidote to a hangover

8. informal keep calm

9. to behave without reserve

10. to show no surprise, anger, fear, etc

11. to make petty and unnecessary distinctions

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hair Scientific  

/ hâr /

1. One of the fine strands that grow from the skin of mammals, usually providing insulation against the cold. Modified hairs sometimes serve as protective defenses, as in the quills of a porcupine or hedgehog, or as tactile organs, as in the whiskers (called vibrissae) of many nocturnal mammals. Hair filaments are a modification of the epidermis of the skin and are composed primarily of keratin. Hair also contains melanin, which determines hair color.

2. A slender growth resembling a mammalian hair, found on insects and other animals.

3. A fine, threadlike growth from the epidermis of plants.

4. See more at trichome

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hair More Idioms  

More idioms and phrases containing hair

• bad hair day
• by a hair
• by the short hairs
• fair-haired boy
• get gray hair from
• hang by a thread (hair)
• hide or hair
• in someone's hair
• let one's hair down
• make one's hair stand on end
• put lead in one's pencil (hair on one's chest)
• split hairs
• tear one's hair
• turn a hair

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Other Word Forms

• dehair
  verb (used with object)
• hairlike
  adjective

Etymology

Origin of hair

First recorded before 900; Middle English heer, Old English hǣr (cognate with Dutch, German haar, Old Norse hār ), with vowel perhaps from Middle English haire “hair shirt,” from Old French, from Old High German hāria (cognate with Middle English here, Old English hǣre, Old Norse hǣra )

Explanation

Hair is the strands of fiber that grow from a person's skin, especially on the scalp. Most mammals, from dogs to bears to mice, also have hair. Your hair might be straight or curly, brown or gray or dark red. Even people with no hair on their heads have body hair, short, fine hairs that grow on arms and legs. Cats have coats that vary too, ranging from hairless to long, silky hair. Even some plants can be described as having hair. Colloquially, people "split hairs," or argue about unimportant things, or tell a "hair-raising" tale, or a spooky story that gives you chills.

Example Sentences

Hair loss is one of the most upsetting side effects of cancer treatment, and many patients look for ways to bring their hair back.

From Science Daily • May 7, 2026

Hair pulling is one of those dark arts which is usually only spotted through video evidence.

From BBC • Apr. 14, 2026

Hair loss associated with COVID-19 infection and with the rapid weight loss resulting from GLP-1 drugs has further fueled patient demand for better treatments with fewer side effects.

From MarketWatch • Feb. 25, 2026

The appeals from the 12, including ex-lawmaker "Long Hair" Leung Kwok-hung and former journalist Gwyneth Ho, were heard last year, and on Monday High Court Chief Judge Jeremy Poon dismissed them.

From Barron's • Feb. 23, 2026

Light Hair was caught by surprise and fell off.

From "In the Footsteps of Crazy Horse" by Joseph Marshall III

Related Words

• eyebrow
• fiber
• fur
• grass
• haircut
• hairstyle
• mane
• sideburn
• strand
• wig
• wool