Fmrita is short for fuck me right in the ass and is used when you see a very good looking boy or you're pretty obsessed with an idol<from a korean group>
e.g. M: Do you see Jay Park?! Oh he'sso hot he can FMRITA.
S: I'm not your friend anymore.
The acronym for: Fuck A Rabid Monkey In The Ass Can be used semi-humorously towards a friend; specificly on IM or other text conversations...in real life you risk sounding extremely geeky.
Guy one: "dude, I just found a hundred dollar bill on the lunch table!!!! you were asking to borrow money the other day right?