A term coined by the great Charlie Kelly meaning someone who possesses inferior intelligence and a lack of common sense, similar to a donkey, or activity that would suggest such.
An insult referring to the absence of wrinkles present in the human telencephalon(cerebrum) -- the largest region of the mammalian brain. Literally implying idiocy at a physiological level.
Someone who is the result of 16 generations of inbreeding therefor lacks any form of intelligence, self awareness and Behaves in hot-headed and impulsive way.
Usually also sociopathic.