brain

1 /breIn/ noun

1 ORGAN (C) the organ inside your head that controls how you think, feel, and move: Messages from the brain are carried by the central nervous system.

2 INTELLIGENCE (U) also brains plural the ability to think clearly and learn quickly: If you had any brains you'd know what I meant.

3 PERSON (C) informal someone who is intelligent, with good ideas and useful skills: Some of our best brains are leaving the country to work in the US.

-see also: brain drain

4 have sth on the brain informal to be always thinking about something: I've got that song on the brain today.

5 be the brains behind sth to be the person who thought of and developed a particular plan, system, or organization, especially a successful one

6 brain dead

a) in a state where your brain has stopped working properly even though your heart may still be beating

b) informal stupid and uninteresting, especially because you live a boring life: If all she does is watch TV all day, no wonder she's brain dead.

7 pick sb's brains to ask someone a lot of questions about something that they know about: I need to pick your brains about this cashflow forecast.

8 brain box BrE informal a very intelligent person

-see also: bird-brained, harebrained, beat your brains out beat 1 (17), rack your brains(s) rack 2 (2) 2 verb (T) spoken to hit someone very hard on the head: I'll brain you if you do that again!