definition of
brain

[1] #1 brain n. [encephalon] that part of the central nervous system that includes all the higher nervous centers; enclosed within the skull; continuous with the spinal cord. wn

[2] #2 brain n. [brainpower, learning ability, mental capacity, mentality, wit] mental ability; "he's got plenty of brains but no common sense". wn

[3] #3 brain n. [mind, head, psyche, nous] that which is responsible for one's thoughts and feelings; the seat of the faculty of reason; "his mind wandered"; "I couldn't get his words out of my head". wn

[4] #4 brain n. [genius, mastermind, brainiac, Einstein] someone who has exceptional intellectual ability and originality; "Mozart was a child genius"; "he's smart but he's no Einstein". wn

[5] #5 brain v. hit on the head. wn