Fym is an acronym for Fuck Your Mindset. This type of slang is typically used within a conversation among peers and teammates within video games who are severely depressed or / are mentally ill.
Ian: I can't do this anymore man, this is too hard for me.
Peter: Man, shut your bitchass up and fym, that negative shit is ruining you from the inside out.
Ian: Sorry dude it's just been pretty rough with these recent matches.
Fym means fuck you mean
John: wanna come over to my house later
Riley: no
John: fym no
Acronym for “fuck you mean”
Friend 1: Man I’m so hungry
Friend 2: Fym you’re so hungry? We ate an hour ago!
FYM
Dude1: Ay foo', do you even fuck?
Dude2: Bro I just fucked yesterday, you filmed that shit!
Dude1: Nah, I didn't do that shit, Stop bullshiting. FYM?
FYM or fym means "fuck you, mate" usually used by british people.
"Mate, you being rude, fym"