A stupid person; it refers to the lack of surface area on an individual's brain. The general thought is that the more surface area (wrinkles, creases, etc.) a brain has, the smarter the person is. Conversely, a person with a smooth brain (no wrinkles) has less surface area and would therefore be stupid.

A term used to reference cannabis/marijuana/weed.

A way of calling somebody very stupid that requires them to be smart, in order to understand.

Opposite of big brain. Smooth brain refers to an idiot or someone dumb. Neuroscientists believe the more folds you have in your brain means the smarter you are. Therefore if you are called smooth brain, you have less folds and therefore dumb.

A derogatory term used to describe someone after they have done something unintelligent, clumsy, or foolish. This term implies a below average intelligence due to an abnormally shaped brain. The expression is used almost exclusively for criticism.

smooth brain- it is someone that is an idiot. this means that the more ripples you have on your brain, the smarter you are. So in conclusion, if you got a smooth brain then you are a dumb ass.