From Longman Dictionary of Contemporary Englishbrainbrain1 /breɪn/ ●●● S2 W2 noun 1 
ORGANorgan [countable]HBHHB the organ inside your head that controls how you think, feel, and move Messages from the brain are carried by the central nervous system. the chemistry of the brain the human brainthe right/left hemisphere of the brain (=the right or left side of the brain) Emotional responses are a function of the right hemisphere of the brain. She died of a brain tumour.brain tissue/cell2 intelligence [countable usually plural, uncountable]INTELLIGENT the ability to think clearly and learn quickly If you had any brains, you’d know what I meant. The job requires brains. Something’s addled your brains (=made you confused). Come on, use your brain, John.3 PERSONperson [countable usually plural] informalINTELLIGENT someone who is intelligent, with good ideas and useful skills Some of our best brains are leaving the country to work in the US. → brain drain4 food [uncountable] (also brains [plural]) the brain of an animal, used as food5 → have something on the brain6 → be the brains behind/of something7 → brain dead8 → something is not brain surgery → bird-brain, hare-brained, → beat your brains out at beat1(22), → pick somebody’s brains at pick1(7), → rack your brain(s) at rack2(2)COLLOCATIONS – Meaning 2: the ability to think clearly and learn quicklyverbshave brainsYou should have more brains than to smoke.use your brainIt’s easy if you just use your brain.rack your brains (=try very hard to think of something)If we all rack our brains we should come up with some ideas.pick somebody’s brains (=ask someone for ideas)I thought I’d pick Greg’s brains about what to take with us.it takes/requires brains to do somethingIt takes brains to think of a plan like that.something addles your brain (=makes you unable to think clearly)The alcohol had addled his brain.adjectivesa good/quick brainIt was obvious that Ann had a good brain.
ORGANorgan [countable]HBHHB the organ inside your head that controls how you think, feel, and move Messages from the brain are carried by the central nervous system. the chemistry of the brain the human brainthe right/left hemisphere of the brain (=the right or left side of the brain) Emotional responses are a function of the right hemisphere of the brain. She died of a brain tumour.brain tissue/cell2 intelligence [countable usually plural, uncountable]INTELLIGENT the ability to think clearly and learn quickly If you had any brains, you’d know what I meant. The job requires brains. Something’s addled your brains (=made you confused). Come on, use your brain, John.3 PERSONperson [countable usually plural] informalINTELLIGENT someone who is intelligent, with good ideas and useful skills Some of our best brains are leaving the country to work in the US. → brain drain4 food [uncountable] (also brains [plural]) the brain of an animal, used as food5 → have something on the brain6 → be the brains behind/of something7 → brain dead8 → something is not brain surgery → bird-brain, hare-brained, → beat your brains out at beat1(22), → pick somebody’s brains at pick1(7), → rack your brain(s) at rack2(2)COLLOCATIONS – Meaning 2: the ability to think clearly and learn quicklyverbshave brainsYou should have more brains than to smoke.use your brainIt’s easy if you just use your brain.rack your brains (=try very hard to think of something)If we all rack our brains we should come up with some ideas.pick somebody’s brains (=ask someone for ideas)I thought I’d pick Greg’s brains about what to take with us.it takes/requires brains to do somethingIt takes brains to think of a plan like that.something addles your brain (=makes you unable to think clearly)The alcohol had addled his brain.adjectivesa good/quick brainIt was obvious that Ann had a good brain. Examples from the Corpus
brain• If you had any brains at all, you wouldn't ask such a stupid question.• Some of the best brains in the country are here tonight.• Branson has an excellent business brain.• The doctors have found a tumor in his brain.• Doctors feared an air rifle pellet had pierced his brain when the joke went horribly wrong.• His brain is completely scrambled tonight.• An algorithm purporting to match what is presumed to be operating in a human brain would need to be a stupendous thing.• My brain worked fast as I tried to decide what to do.• Ted's got more money than brains.• But the brain is surrounded by the skull, and all that escaped blood takes up space, squeezing the brain.• As our discussion of the brain revealed, alcohol affects nearly everything it touches.• A tumour or trauma in one side of the brain causes a loss in the field of vision on the other side.• They also accept that the brain has certain innate dispositions, if only the disposition to be reinforced by particular stimuli.• Louis was the brain in our class.• The brain has trillions of cells.brain tissue/cell• The sequelae of hypertonicity are believed to result largely from changes in brain cell size.• A biopsy of brain tissue detected the presence of toxoplasmosis, which is relatively harmless in people with normally functioning immune systems.• Presumably the metabolism of brain cells is disrupted and some cells die.• But once converted into prions, they turn deadly, destroying the brain tissue.• The alcohol is now affecting her balance and slowing the brain cells governing learned social behaviour and inhibitions.• You pay for the service with brain cells instead of money, and everyone has simply billions of brain cells on deposit.use ... brain• A number of different neurotransmitter substances are used in brains.• Just to be using brain and muscles and feelings all together at once, and not failing.• He began to take pride in using his brains to avoid trouble.• Receptors come in dozens of varieties, each specially designed to accommodate one of the dozens of neurotransmitters used by the brain.• Today, they primarily use their brains.• These chemical studies have now been complemented by the use of brain scanners.• Monkeys have a minor version of our tendency to use the left brain for listening carefully to rapid sound sequences.• Terry offered a bike to his son if only he would use the good brain he undoubtedly possessed.brainbrain2 verb [transitive] informal HITto hit someone very hard on the head – used humorously I wanted to brain him.→ See Verb tableExamples from the Corpus
brain• I'll brain you if you don't shut up!Origin brain1 Old English brægen 