look up any word, like half chub:
 
1.
fuck it i'm young
more commonly used on the internet that in real life.
online conversation-

friend- you out tonight?
me- i wasn't going to but fiiy!
by Bethany-Ruth July 07, 2012
 
2.
The acronym for the phrase 'Fuck It I'm Young'. It's infinitely better than YOLO and much easier to pronounce, obviously.
Matt: You shouldn't eat pumpkin soup whilst recording the podcast mate
Cailem: FIIY
by Steven. Just Steven. August 17, 2012
 
3.
Fuck - It - I'm - Young

Justification for doing anything immature, stupid, dangerous or ridiculous
Jimmy: I dunno man, do you really think you should fuck this dead hooker we found here in the forest

Billy: FIIY

Jimmy: Hmm didn't think of it like that, Seems legit
by SmilesNLulz May 27, 2012