To wash yourself with a flannel starting with your Face, then Armpits and lastly Fanny.
Gf: I can’t be arsed to shower I’m going to have a faf.
Bf: Ok bruh
Becky won’t go to the bars with me at 1am on a Wednesday she’s a FAF
1. Fat As Fuck is what i've always used it as, however, apparently it can also stand for:
2. Fit As Fuck