brain

BRAYN/bɹeɪn/

13 meanings of brain

1
body organnouncountable or uncountable
The control center of the nervous system, located in the skull, responsible for perception, thought, memory, emotion, and action.
Oxygen deprivation can cause the brain to suffer permanent damage within minutes.
Researchers scanned each patient's brain to locate the affected region.
2
mindnouncolloquialcountable or uncountable
A person's mind: the seat of thought, awareness, and ideas.
That strange image has been stuck in my brain all day.
With the exam tomorrow, my brain is too full of formulas to let me sleep.
UsageOften with in or on: stuck in my brain. Have something on the brain means you keep thinking about it.
Similarmind, head
Note
Here the organ stands for what it holds, such as worries, images, and plans. The sense is casual in phrases like too much on my brain, but it is not only colloquial. Tennyson's In Memoriam (1850) wonders "what possess'd my brain", in a register far from chatty. Brain makes the thought sound more physical, as if it were lodged somewhere.
Checked 2 Nov 2026 · 2 facts
Alfred Tennyson wrote In Memoriam, first published in 1850. en.wikisource.org
In Memoriam contains the words 'what possess'd my brain'. gutenberg.org
3
thinking powernouncountable or uncountableplural
Mental or intellectual ability, often in the plural brains; the capacity to reason, learn, and understand, in general or for a particular task.
Solving the riddle took more brains than brawn.
He relied on his brain rather than his strength to win the contest.
Similarintelligence, intellect, mind, wit
4
part of organnouncountable or uncountable
A region of the brain, especially one linked to particular mental functions or abilities.
The limbic brain governs much of our emotional response.
Studies of the social brain reveal how we read other people's intentions.
UsageUsually with a describing word: the left brain, the social brain.
Note
Because each region counts as a brain of its own, a writer can speak of a person's several brains. William Irwin Thompson's The Time Falling Bodies Take to Light (1981) describes "the three brains of man."
Checked 2 Nov 2026 · 3 facts
William Irwin Thompson wrote The Time Falling Bodies Take to Light. openlibrary.org
The book was first published in 1981. openlibrary.org
The book contains the exact phrase "the three brains of man." en.wiktionary.org
5
chief plannernouncolloquialcountable or uncountableplural
The person who supplies the intelligence or planning behind an effort or organization.
He was the brain behind the company's most successful product launch.
Everyone knew the quiet accountant was the brains behind the robbery, though he never left his office.
UsageUsually the brains behind something; for one person the verb stays singular: she is the brains of the team.
Similargenius, thinker, mind

Less common meanings

6
smart personnouncolloquialcountable or uncountable
A highly intelligent person.
Only a real brain could have cracked that code so quickly.
The new hire turned out to be a brain who solved problems no one else could.
Similargenius, thinker, intellectual, egghead, brainiac
Oppositeidiot, dunce, dimwit
7
think clearlyverbnonstandardhumorousintransitive
To think effectively or clearly.
It's far too early in the day for me to brain properly.
After the long flight, she simply couldn't brain anymore.
UsageMostly negative or in the -ing form: I can't brain today; my brain isn't braining.
Similarthink, function, concentrate
8
computer partnouncountable or uncountable
The calculating part of a machine or computer, named by analogy with the human brain.
The drone's brain processes data from a dozen sensors at once.
Engineers replaced the machine's brain with a faster processor.
Similarprocessor, controller, computer
9
hit on headverbtransitive
To strike someone hard on the head, sometimes hard enough to kill them by crushing the skull.
The robber tried to brain the guard with a crowbar.
He brained the intruder with a heavy candlestick.
UsageUsually brain someone with an object: brained him with a lamp.
Similarbludgeon, club, bash
Note
The blow can kill, but it need not. In K.J. Charles's Think of England (2014), a wife brains her husband with a table lamp, and he ends up needing treatment for a fractured skull.
Checked 2 Nov 2026 · 3 facts
K.J. Charles wrote Think of England, first published in 2014. kjcharleswriter.wordpress.com
In the novel, Mrs. Lambdon brains her husband with a table lamp. en.wiktionary.org
The husband needs medical attention for a fractured skull. en.wiktionary.org
10
oral sexnounslangvulgaruncountable
Oral sex; sexual stimulation performed with the mouth.
They argued because he expected brain every single night.
She said she'd give brain only if he treated her right.
UsageUsed without a: give brain, get brain.
Similarhead, blowjob
Note
Hip-hop lyrics carry this vulgar slang sense, as in Kanye West's "Good Life" (2007). Because the plain word sounds innocent, the explicit meaning can catch listeners off guard.
11
verbobsoletetransitive
To conceive of something in the mind; to understand it.
'Tis still a dream, or else such stuff as madmen / Tongue, and brain not.
1611, William Shakespeare, “The Tragedie of Cymbeline”
Note
Shakespeare's Cymbeline (first printed in 1623) gives the sense its clearest setting: "such stuff as madmen / Tongue, and brain not". These are words spoken without being understood. The pairing with tongue shows the idea: to brain something was to take it in with the mind.
Checked 2 Nov 2026 · 1 fact
Tongue and brain not means speaking without understanding. shakespearenj.org
12
verbobsolete
To destroy something; to put an end to it.
He was going on with some wild reminiscences about his tomahawk-pipe, which, it seemed, had in its two uses both brained his foes and soothed his soul, when we were directly attracted to the sleeping rigger.
1851, Herman Melville, Moby-Dick
13
noun
A removable top compartment of a backpack that straps over the top opening.

Practice

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Origin

From Middle English brayn, from Old English bræġn ('brain'), from Proto-Germanic *bragną, probably ultimately from a Proto-Indo-European root meaning 'skull, brain'. It is related to Dutch brein, West Frisian brein, and Low German Bregen.

Checked 31 Oct 2026 · 5 facts

Brain derives from Middle English brayn. en.wiktionary.org
Middle English brayn derives from Old English bræġn. en.wiktionary.org
Old English bræġn means 'brain'. en.wiktionary.org
Old English bræġn derives from reconstructed Proto-Germanic *bragną. en.wiktionary.org
Brain is related to Dutch brein, West Frisian brein, and Low German Bregen. en.wiktionary.org