Meaning of “brain” - Learner’s Dictionary

brain

noun uk us /breɪn/
ORGAN [ C ]

A2 the organ inside your head that controls your thoughts, feelings, and movements:

brain damage
PERSON [ C ] informal
brains

intelligence:

He has brains and good looks.
have sth on the brain informal

to think or talk about something all the time:

You have football on the brain!
the brains behind sth informal

the person who has planned and organized something successful:

Anthony is the brains behind the project.

(Definition of “brain” from the Cambridge Learner’s Dictionary © Cambridge University Press)