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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.
Zoology. (in many invertebrates) a part of the nervous system more or less corresponding to the brain of vertebrates.
Sometimes, brains. (used with a plural verb) understanding; intellectual power; intelligence.
the brain as the center of thought, understanding, etc.; mind; intellect.
brains, Slang. a member of a group who is regarded as its intellectual leader or planner:
The junior partner is the brains of the firm.
Informal. a very intelligent or brilliant person.
Informal.

the controlling or guiding mechanism in a computer, robot, pacemaker, etc.
the part of a computer system for coordination or guidance, as of a missile.

to smash the skull of.
Slang. to hit or bang (someone) on the head.
beat one’s brains out, Informal. to try very hard to understand and work out a problem, remember something, etc.:
She beat her brains out studying for the exam.
have something on the brain, to have an obsession; be occupied with:
Lately I seem to have food on the brain.
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.
noun
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 Technical name encephalon, related adjectives cerebral encephalic
the main neural bundle or ganglion of certain invertebrates
(often pl) (informal) intellectual ability: he’s got brains
(informal) shrewdness or cunning
(informal) an intellectual or intelligent person
(usually pl; functioning as singular) (informal) a person who plans and organizes an undertaking or is in overall control of an organization, etc
an electronic device, such as a computer, that performs apparently similar functions to the human brain
on the brain, constantly in mind: I had that song on the brain
pick someone’s brain, to obtain information or ideas from someone
verb (transitive)
to smash the skull of
(slang) to hit hard on the head
n.

Old English brægen “brain,” from Proto-Germanic *bragnam (cf. Middle Low German bregen, Old Frisian and Dutch brein), from PIE root *mregh-m(n)o- “skull, brain” (cf. Greek brekhmos “front part of the skull, top of the head”). But Liberman writes that brain “has no established cognates outside West Germanic …” and is not connected to the Greek word. More probably, he writes, its etymon is PIE *bhragno “something broken.”

The custom of using the plural to refer to the substance (literal or figurative), as opposed to the organ, dates from 16c. Figurative sense of “intellectual power” is from late 14c.; meaning “a clever person” is first recorded 1914. Brain teaser is from 1923. Brain stem first recorded 1879, from German. Brain drain is attested from 1963. An Old English word for “head” was brægnloca, which might be translated as “brain locker.” In Middle English, brainsick (Old English brægenseoc) meant “mad, addled.”
v.

“to dash the brains out,” late 14c., from brain (n.). Related: Brained; braining.

brain (brān)
n.
The portion of the central nervous system that is enclosed within the cranium, continuous with the spinal cord, and composed of gray matter and white matter. It is the primary center for the regulation and control of bodily activities, receiving and interpreting sensory impulses, and transmitting information to the muscles and body organs. It is also the seat of consciousness, thought, memory, and emotion. Also called encephalon.
brain
(brān)

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. See more at brainstem, cerebellum, cerebrum.

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

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.

verb phrase

To labor strenuously with the mind, often with a sense of having failed: I beat my brains out getting ready for it, but flunked anyway (late 1500s+)
To beat someone severely: threatened to beat my brains out

noun

An intelligent person; intellectual; good scholar: The publicity of being a brain did not further her movie career as a glamour girl (1914+)

verb

To injure with a hard blow to the head •Attested fr 1382 in the full sense, ”kill by knocking out the brain”: The left hook really brained him

Related Terms

birdbrain, bubble brain, have something on the brain, lamebrain, not have brain one, pick someone’s brain, rattlebrain, scatterbrain
Make a great mental effort to understand, solve, or remember something, as in Joe’s beating his brains out to finish this puzzle . Christopher Marlowe used this hyperbolic idiom in The Massacre of Paris (1593): “Guise beats his brains to catch us in his trap.” Also see rack one’s brains

brain drain
brain someone
brain trust