F.

F.2.M. - Female "To" Male
F.2.N. - Female "To" Neutral
F.A.R.T. - Feminist Appropriating Reactionary/Ridiculous Transphobe
Femboy - Typically refers to an individual who identifies as a boy/man, but presents in a feminine manner.
F.F.S. - Facial Feminization Surgery
F.H.T. - Feminizing Hormone Therapy
Fishmouth - A type of FTM top surgery.
F.M.S. - Facial Masculinization Surgery
F.P.B. - Female Pattern Baldness
F.T.M. - Female To Male
F.T.N. - Female To Neutral