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¹brain

noun \ˈbrān\

: the organ of the body in the head that controls functions, movements, sensations, and thoughts

: the ability to think and reason

: a very intelligent person

Full Definition of BRAIN

a : the portion of the vertebrate central nervous system enclosed in the skull and continuous with the spinal cord through the foramen magnum that is composed of neurons and supporting and nutritive structures (as glia) and that integrates sensory information from inside and outside the body in controlling autonomic function (as heartbeat and respiration), in coordinating and directing correlated motor responses, and in the process of learning — compare forebrain, hindbrain, midbrain

b : a nervous center in invertebrates comparable in position and function to the vertebrate brain

a (1) : intellect, mind <has a clever brain> (2) : intellectual endowment : intelligence —often used in plural <plenty of brains in that family>

b (1) : a very intelligent or intellectual person (2) : the chief planner within a group —usually used in plural <she's the brains behind their success>

: something that performs the functions of a brain; especially : an automatic device (as a computer) for control or computation

See brain defined for English-language learners

See brain defined for kids

Illustration of BRAIN

Origin of BRAIN

Middle English, from Old English brægen; akin to Middle Low German bregen brain, and perhaps to Greek brechmos front part of the head

First Known Use: before 12th century

Related to BRAIN

Synonyms: genius, brainiac, intellect, thinker, whiz, wiz, wizard

Antonyms: blockhead, dodo, dolt, dope, dumbbell, dummy, dunce, fathead, goon, half-wit, hammerhead, idiot, imbecile, knucklehead, moron, nitwit, numskull (or numbskull), pinhead

Other Anatomy Terms

bilateral symmetry, carotid, cartilage, dorsal, entrails, prehensile, renal, solar plexus, supine, thoracic, ventral

Rhymes with BRAIN

ain, Aisne, ane, Bain, bane, blain, cane, chain, crane, deign, drain, fain, fane, feign, gain, grain, Kane, lane, Lane, main, mane, pain, Paine, pane, plain, plane, quean, rain, reign, rein, sain, sane, seine, Seine, skein, Spain, sprain, stain, strain, swain, thane, thegn, train, twain, Twain, vain, vane, vein, wain, wane, Wayne

²brain

verb

: to hit (someone) on the head very hard

Full Definition of BRAIN

transitive verb

: to kill by smashing the skull

: to hit on the head

See brain defined for English-language learners

First Known Use of BRAIN

14th century

BRAINS Defined for Kids

¹brain

noun \ˈbrān\

Definition of BRAIN for Kids

: the part of the nervous system that is inside the skull, consists of grayish nerve cells and whitish nerve fibers, and is the organ of thought and the central control point for the nervous system

: the ability to think : intelligence

: someone who is very smart

²brain

verb

brainedbrain·ing

Definition of BRAIN for Kids

: to hit on the head very hard

Medical Dictionary

brain

noun \ˈbrān\

Medical Definition of BRAIN

: the portion of the vertebrate central nervous system enclosed in the skull and continuous with the spinal cord through the foramen magnum that is composed of neurons and supporting and nutritive structures (as glia) and that integrates sensory information from inside and outside the body in controlling autonomic function (as heartbeat and respiration), in coordinating and directing correlated motor responses, and in the process of learning—see forebrain, hindbrain, midbrain

: a nervous center in invertebrates comparable in position and function to the vertebrate brain