Almost crazy. Bordering on "mental," which is completely
insane.
One who acts like a retard, even though he does not have a condition of mental retardation.
Dude, I can't stand living with
Jake anymore. He sits in the living room doing
hot rails and playing World of Warcraft all day. I mean... the
guy is driving me half mental!
That new kid is half mental. He smells like burnt onions, he can't dress himself and he always has mustard stains on his shirt.