We all know what a brain is. A doctor will tell you that the brain is the organ of the body in the head. It controls our body's functions, movements, feelings and thoughts.
But a brain can mean so much more.
A brain can also simply be a smart person. If a person is called brainy, she is smart and intelligent. And if you are the brains behind something, you are responsible for developing or organizing something. For example, Bill Gates is the brains behind Microsoft.
A brain trust is a group of experts who give advice.
To tease is to make fun of someone. But a brainteaser is not one who makes fun of someone else's brain. A brainteaser is a riddle or puzzle that makes you think.
Brain drain is when a country's most educated people leave their countries to live in another.
A brainchild is an idea that one has without any help from others. If you have a really great idea, it is your brainchild—no one else's.
However, if many people are responsible for a great idea, they brainstormed it. Brainstorm is a process of thinking creatively. But if you can't find a solution to a problem, or if you can't even remember what the problem is, you may have to rack your brains, which means to think very hard about something.
To pick someone's brain is quite different. When you meet someone who knows a lot about a subject you like, you may want to pick his brain to learn more.
Now, if people are brainwashed,it does not mean their brains are nice and clean. To brainwash means to make someone accept new beliefs by using repeated pressure in a forceful or tricky way. And brainwash is never used in a positive way.