Finger Activated Stud: A guy that needs someone, usually his girlfriend, to finger his asshole in order for him to get turned on and achieve orgasm.
Tina: Hi Tammy, how's it going with your new boyfriend?
Tammy: Gosh Tina... I don't know about him. He's great, but he's a FAS.
Tina: You mean you had to finger his ass?
Tammy: That's right, and I think I lost one of my Lee Press-on nails inside him!