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

Jason died May 12, 2026, of brain cancer.

From Los Angeles Times ● Aug. 23, 2026

"We found fundamental changes in brain circuits occurring in young mice that still had normal learning and memory, and importantly, that those changes predicted the development of cognitive deficits at older ages."

From Science Daily ● Aug. 23, 2026

Earlier research had already found signs of unusually high brain activity in human APOE4 carriers before middle age.

From Science Daily ● Aug. 23, 2026

This allowed the researchers to estimate what typical brain connectivity looks like at different points in life.

From Science Daily ● Aug. 22, 2026

A brain "address" can specify left or right hemisphere, the lobe, the nearest ridge or fold, and whether the location is on top or bottom, inside or out, and front or back.

From "Phineas Gage" by John Fleischman

Those who spoke three languages had brains that appeared about seven years younger.

From Science Daily ● Aug. 22, 2026

The brains who powered China’s surprising AI leap.

From MarketWatch ● Aug. 21, 2026

Until now, however, scientists have had a limited understanding of exactly where synaptic loss occurs in the brains of living people because conventional imaging methods such as magnetic resonance imaging cannot specifically measure synapses.

From Science Daily ● Aug. 20, 2026

Normally these organoids live for a few months, meaning they can only offer a window into the earliest stages of human brains, which take nearly 20 years to fully develop.

From Barron's ● Aug. 19, 2026

“She’ll listen to you. She says you have the brains of the family—you and William. Of course...”

From "Carry On, Mr. Bowditch" by Jean Lee Latham

Larger brained animals could use their intelligence to find fruit more efficiently, which in turn provided more energy to fuel a larger brain.

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

A second major find, the nearly complete skull of a larger brained hominid, long known simply by its field number “1470” and now classified as H. rudolfensis, bolstered that point.

From Science Magazine ● Jan. 2, 2022

Raizel and I scooted out of the way to avoid being brained by one.

From "The City Beautiful" by Aden Polydoros

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

The second was a deep gully, but so choked with rubble that after nearly braining myself I desisted.

From Prester John by John Buchan

"I guess that was nigh braining the child," quoth Miss Amanda, with the greatest coolness, and without making the least apology.

From Roughing It in the Bush by Susanna Moodie

That is the Tessino, braining itself in cataracts.

From Bohemian Days Three American Tales by George Alfred Townsend

Related Words

• head
• intellect
• mind