brain

that part of the central nervous system that includes all the higher nervous centers; enclosed within the skull; continuous with the spinal cord

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

mental ability

he's got plenty of brains but no common sense

the brain of certain animals used as meat

someone who has exceptional intellectual ability and originality

Mozart was a child genius

he's smart but he's no Einstein

kill by smashing someone's skull

hit on the head