brain

American  

[breyn] / breɪn /

noun

brains plural

1. Anatomy, Zoology. the part of the central nervous system enclosed in the cranium of humans and other vertebrates, consisting of a soft, convoluted mass of gray and white matter and serving to control and coordinate the mental and physical actions.

2. Zoology. (in many invertebrates) a part of the nervous system more or less corresponding to the brain of vertebrates.

3. (used with a plural verb) Sometimes brains. understanding; intellectual power; intelligence.

   Synonyms:

   capacity, sense

4. the brain as the center of thought, understanding, etc.; mind; intellect.

5. Slang. brains, a member of a group who is regarded as its intellectual leader or planner.

   The junior partner is the brains of the firm.

6. Informal. a very intelligent or brilliant person.

7. Informal.

   1. the controlling or guiding mechanism in a computer, robot, pacemaker, etc.

   2. the part of a computer system for coordination or guidance, as of a missile.

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verb (used with object)

brains, present (3rd person singular) brained, past participle, past braining present participle

1. to smash the skull of.

2. Slang. to hit or bang (someone) on the head.

idioms

1. beat one's brains out, to try very hard to understand and work out a problem, remember something, etc..

   She beat her brains out studying for the exam.

2. have something on the brain, to have an obsession; be occupied with.

   Lately I seem to have food on the brain.

3. pick someone's brains, to obtain information by questioning another person rather than by seeking it independently.

   He refused to prepare for the exam but counted on being able to pick his roommate's brains.

brain British  

/ breɪn /

noun

1. Technical name: encephalon.  the soft convoluted mass of nervous tissue within the skull of vertebrates that is the controlling and coordinating centre of the nervous system and the seat of thought, memory, and emotion. It includes the cerebrum, brainstem, and cerebellum

2. the main neural bundle or ganglion of certain invertebrates

3. informal (often plural) intellectual ability

   he's got brains

4. informal shrewdness or cunning

5. informal an intellectual or intelligent person

6. informal (usually plural; functioning as singular) a person who plans and organizes an undertaking or is in overall control of an organization, etc

7. an electronic device, such as a computer, that performs apparently similar functions to the human brain

8. constantly in mind

   I had that song on the brain

9. to obtain information or ideas from someone

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verb

1. to smash the skull of

2. slang to hit hard on the head

brain Scientific  

/ brān /

1. The part of the nervous system in vertebrates that is enclosed within the skull, is connected with the spinal cord, and is composed of gray matter and white matter. It is the control center of the central nervous system, receiving sensory impulses from the rest of the body and transmitting motor impulses for the regulation of voluntary movement. The brain also contains the centers of consciousness, thought, language, memory, and emotion.

2. See more at brainstem cerebellum cerebrum

3. A bundle of nerves in many invertebrate animals that is similar to the vertebrate brain in function and position.

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brain Cultural  

1. The central organ in the nervous system, protected by the skull. The brain consists of the medulla, which sends signals from the spinal cord to the rest of the brain and also controls the autonomic nervous system; the pons, a mass of nerve fibers connected to the medulla; the cerebellum, which controls balance and coordination; and the cerebrum, the outer layer of which, the cerebral cortex, is the location of memory, sight, speech, and other higher functions. The cerebrum contains two hemispheres (the left hemisphere and the right hemisphere), each of which controls different functions. In general, the right hemisphere controls the left side of the body and such functions as spatial perception, whereas the left hemisphere controls the right side of the body and functions such as speech. Under the cerebral cortex are the thalamus, the main relay center between the medulla and the cerebrum; and the hypothalamus, which controls blood pressure, body temperature, hunger, thirst, sex drive, and other visceral functions.

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brain More Idioms  

More idioms and phrases containing brain

• beat one's brains out
• blow one's brains out
• on one's mind (the brain)
• pick someone's brains
• rack one's brains

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Usage

What is a basic definition of brain? The brain is the organ in humans and animals that’s responsible for thought processes. The plural form brains refers to intelligence or a person who is the smartest member of a group. The word brain has several other senses as a noun and a few as a verb. Your brain is a squishy organ located inside your head and is protected by your skull. The brain is highly complex. It is the seat of all your conscious thoughts and unconscious impulses and is like the control center of the body, allowing you to do things like speak, move your muscles, and breathe without thinking. The brain, spinal cord, and nerves make up the nervous system. Real-life examples: You and every other person have a brain. Animals have brains too, although they aren’t capable of doing all of the things the human brain is able to do. Your brain is very important and has a vast number of jobs, such as keeping all of your memories, telling your other organs what to do, and helping you read these words. Used in a sentence The brain is the most complex and perhaps the most studied organ.  The plural form brains is used as a term for intelligence or intellect. This usage alludes to the brain being the organ that handles thinking. Real-life examples: You may have heard a person being described as having brains. This means they are smart and able to figure things out, especially difficult or complex problems. Used in a sentence: I have to study hard to do well in math, but my sister has brains and aces her tests without studying. Relatedly, a person who is considered very smart can be called a brain. Used in a sentence: None of us could figure out the computer problem so we called in Mike, who was a real brain when it comes to fixing them. Brains is also used to refer to the smartest member or members of a group or team, especially the one who comes up with plans. Real-life examples: Movies and shows that feature a heist or a plan often have a person who is referred to as the “brains of the operation.” For example, scientist Bruce Banner often comes up with plans or solutions for the Avengers (when he isn’t getting angry and turning into the Incredible Hulk). In the Harry Potter series, Hermione is definitely the brains of the trio that she forms with Harry and Ron. Used in a sentence: Everyone knew that Edd was the real brains behind the money-making schemes.

Synonym Usage

See mind.

Other Word Forms

Derived Forms

• superbrain
  noun
• brainlike
  adjective

Inflected Forms

Nouns

• brains
  plural

Participles

• braining
  present
• brained
  past

Conjugated Forms

Present

• brain
  simple
• brains
  simple
• have brained
  perfect
• has brained
  perfect
• am braining
  progressive
• are braining
  progressive
• is braining
  progressive
• have been braining
  perfect progressive
• has been braining
  perfect progressive

Past

• brained
  simple
• had brained
  perfect
• was braining
  progressive
• were braining
  progressive
• had been braining
  perfect progressive

Future

• will brain
  simple
• will have brained
  perfect
• will be braining
  progressive
• will have been braining
  perfect progressive

Etymology

Origin of brain

First recorded before 1000; Middle English; Old English bræg(e)n, bregen; cognate with Low German brägen, Dutch brein; akin to Greek brégma; see bregma ( def. )

Explanation

The brain is the most complex organ in the body, located inside the protective skull. The word can also be used as a verb in the phrase "to brain," which means to injure or kill someone by hitting them in the head. The human brain has inspired many idioms, or colorful phrases. Thinking intently (or obsessively) about something means that you've got it "on the brain," and to "pick someone's brain" means to get their ideas on something. A puzzle is a "brainteaser, someone smart is called "a brain," and the person who runs something is said to be "the brains" of the operation.

Example Sentences

See Examples For:

brain brains brained braining

Read: Can China just steal America’s AI brain that’s costing trillions to develop?

From MarketWatch ● Jul. 17, 2026

It’s hard not to feel some kind of sympathy for Max, who sustained a severe brain injury while he was incarcerated that required surgeons to install a metal plate in his skull.

From Salon ● Jul. 17, 2026

That difference helped the sugar-coated particles accumulate more heavily in tumors after crossing into the brain.

From Science Daily ● Jul. 17, 2026

"I can't accept this diagnosis knowing we could be doing so much more in Scotland to support people with brain cancer."

From BBC ● Jul. 17, 2026

Aristotle, the greatest scientist of his time, "knew" that the primary function of the brain was to cool the blood.

From "Phineas Gage" by John Fleischman

But the genre also requires action, adventure, enlightenment, struggle, the guest-host relationship observed by the ancients and the supremacy of brains over brawn.

From The Wall Street Journal ● Jul. 16, 2026

Experts say young people can be more sensitive to caffeine as they have smaller bodies and their brains are still developing.

From BBC ● Jul. 16, 2026

For now, there is a lack of large-scale, long-term studies to judge the true impact of the new technology on human brains, researchers agreed.

From Barron's ● Jul. 15, 2026

You start to realize that it’s kind of rewired people’s brains.

From Salon ● Jul. 5, 2026

“Well done, squirrel. Very clever indeed. I could use someone like you in my army. Somebody smart, with brains like yours.”

From "Redwall" by Brian Jacques

That way, it won’t turn into a brained brick because of a human error somewhere in northern Virginia.

From Los Angeles Times ● Oct. 23, 2025

They found that the larger brained primate species did not solve the fruit-finding puzzle more efficiently than smaller brained mammals.

From Science Daily ● May 28, 2024

Clevinger, his long hair brained into pigtails, allowed three runs, two earned, and six hits in 4 1/3 innings while striking out six and walking two.

From Seattle Times ● May 10, 2022

At least there’s nothing pointy on the Steam Deck, unlike some of the book corners I’ve brained myself with over the years.

From The Verge ● Mar. 29, 2022

No, it was meant to determine if you were right brained or left brained, usually connoted by handedness.

From "Nine, Ten: A September 11 Story" by Nora Raleigh Baskin

We are a long way here from Thor developing the wheel or the Fat Broad braining the Snake.

From Time Magazine Archive

It was something that they prevented the mace of chivalry from utterly braining humankind.

From Lippincott's Magazine of Popular Literature and Science Volume 17, No. 097, January, 1876 by Various

Early after breakfast on that morning,—that morning on which Tappitt had for a moment thought of braining Luke Rowan with the poker,—Mrs. Ray started from the cottage on her mission into Baslehurst.

From Rachel Ray by Trollope, Anthony

"Théo is at home—he went to tell his mother," Joyselle said, nearly braining an old lady with his violin-case as he swung round to speak.

From The Halo by Justice, B. Martin

Oh the demons, they were cackling while he sat devouring a great moose joint, until he was close to braining them with the yellow ball of the joint.

From The Best Short Stories of 1917 and the Yearbook of the American Short Story by O'Brien, Edward J. (Edward Joseph Harrington)

Related Words

• head
• intellect
• mind