brain

brain or brains [brān]

n.

[ME < OE brægen < IE base * mregh-m(n)o-, skull, brain > Gr bregma, forehead]

1. [sometimes pl.] the mass of nerve tissue in the cranium of vertebrate animals, an enlarged extension of the spinal cord: it is the main part of the nervous system, the center of thought, and the organ that perceives sensory impulses and regulates motor impulses: it is made up of gray matter (the outer cortex of nerve cells) and white matter (the inner mass of nerve fibers)

2. a comparable organ in invertebrate animals

3.

a) [often pl.] intelligence; mental ability

b) Informal a person of great intelligence

4. [usually pl.] Informal the main organizer or planner of a group activity; chief controller or director

vt.

1. to dash out the brains of

2. Slang to hit hard on the head

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beat one's brains or rack one's brains or cudgel one's brains

to try hard to remember, understand, or solve something

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have on the brain

to be obsessed by

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pick someone's brains or pick someone's brain

to extract information, ideas, etc. from someone and use to one's own advantage