1. Describes a hellishly hideous person.
2. The final stage of ugly.
3. Short for "Motherfucking ugly."
4. The state of which one becomes when one gets too hype in any situation, caused by crumpling of the face.
1. That bitch is muthafugly!
2. Yo, that baby isn't ugly
! It's muthafugly!
3. Joe: You're motherfucking ugly.
Jim: Dude, just say muthafugly.
Joe: Oh, ok!
4. Hey, look at Dave getting muthafugly on the dance floor!
A person so hideous they are not just fugly, they have been elevated to the highest tier of ugliness. It is a top echelon of raunchiness, no other word can fill. Only to be used as a last ditch effort to describe someone.
"There's the good, the bad, the fugly, and then the dreaded, muthafugly."
"That chick is so muthafugly, my eyes burn."