Raisin Brain
A very impaired brain, shrunk and deformed - like a grape withered by the sun, forming a raisin.
They always wondered what was wrong with Chad, he always seemed dumber than a piece of toast. "Perhaps he has a raisin brain?" Julie offered. "My cousin had raisin brain." George said. "Couldn't tell his ass from his face." Chad continued to stare at them in confused silence.