Fit As Fuck.
This acronym for the term was coined in Essex, England, and since then has been frequenly used by the whole teenage age group, especially those in the Alternative music scene. It can quite commonly be found on Myspace, a popular internet socialising website.
Please note: F.A.F. has a dot after the second F to add emphasis. The conventional F.A.F is more widely used. The extra dot may also added to avoid the certain 'chaviness' surrounding the more common form.
It also quite acceptable to use F.A.F. in normal speach.
F.A.F. You have preety eyes dear.
Richard: Qwoar, that new Art teacher is preety tastey yeah?
Ross: She's F.A.F. mate. Better get better at painting!