Fm sometimes means "For me", "For my" and maybe even "Fuck me"
It's the way you read it makes sense
(For my) I'm waiting fm little brother to get the fuck off my Xbox.
(For me) Fym?? 2nd period just ended fm. -a past conversation I had using "fm"
(Fuck me) Fuck me bruh ...
FM's are a commonly used slang for fake money
Ayo don't mix your FM's with your other bread or you fuck up and get bagged.
Full mana. Your mystical energies are fully available and you're ready to cast some spells.
Person 1: How are you doing on your mana levels, casters?
Caster: FM here, ready to sling some spells!
Fucking machine.
It's used in reference to a person who would you fuck repeatedly.
"Bro, that girl is such an FM, damn, wish I had a chance!"