An insult worse than the likes of "your mom". Often used by those with a higher intelligence or beauty than the victem of the verbal assult. Derived from fat (an over eating side effect)and medusa (that bitch in greek mythology).
"Why you bein' such a bitch Kimberly?"

"Shut yo face you Fat Medusa!"

"Oooooooooo..."
by DVD Player April 10, 2008
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