idioms brain 3
blow brains out (kill with a shot in the head): Put your gun down or I’ll blow your brains out.
brainstorm (a clever idea AmE): The problem is unsolvable, unless someone has a brainstorm.
brainstorm (a sudden inability to think clearly or act BrE): I had a brainstorm in the exam and didn’t even answer a single question.
brainwave (a clever idea BrE): I’ve had a brainwave, I know what we should do.
cudgel your brains (think very hard): I have to cudgel my brains to find a solution.
pea-brained (a very stupid person): He’s just another pea-brained idiot.
rack your brain (think very hard): It’s not so easy. You have to rack your brains once you start on it.
the brains behind (the person who provides ideas and plans for an activity): He was the brains behind the bank robbery.