NOT a substitute for the eff-word.
Can be used to get attention from friends or others, can be said; Fut, Futting, FUT-UH, mmmmmmmmmmmFUT.
Zach: Uh, yo. FUT! (Gets Johns attention)
John: Hey Zach, hows it going?
Brandon: Yo, last night was futting insane.
Mike: Yeah, I can't believe you hooked up with that DONKEY.