sister fister a brother or even a sister that likes to casualy fist their sister up the vagina or even the arse hole. Most of the time resulting in a very sore vagina/anus, and if caught resulting in a sentence of 10 years in jouvey.
(here is a role-play of a sister fister and his sister) Kirsten after a long sleep Kirsten: o hi there Aaron i didnt see you over there in that dark corner. Aaron: You dont need to see me, you just need to feel me Aaron and Kirsten both grin and Kirsten turns around
Strictly, one who indulges in a particular form of incest, using only their hand (see fister. Often used as a term of contempt, and shortened to "sissy" on account of their unadventurousness.
A word used for respecting whamen so people will not get triggered by your clickbaity and 10:01 long videos