What is ff transsexual?

Perhaps it means full-fledged. Meaning that someone is more than just a drag queen or crossdresser. If a person has no desire for surgery, then they were likely not born with transsexualism. Many people have corrupted the term transsexual to include many who don't have transsexualism, so many with it use qualifiers before the term such as real, true, genuine, full-fledged, mainstreamist, assimilationist, etc.

Now, if you mean FFS, that is short for feminizing facial surgery.