sisterfister 

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.

See also brotherfucker.

Your brother's such a sisterfister, you know.

sisterfister by Lucifer B September 20, 2005

Sisterfister 

Adjective meaning an alternative, clean version to Mother Fucker

*joey smacking Sarah on the butt
Sarah - "Ouch you sisterfister"

Sisterfister by Hink68PMMF October 25, 2017

Sisterfister 

its the female of rare species called brofister, it was discovered in youtupia jungles at 2017 by the famous scientist felix kelberg pergananet

and always sisterfister!!!!

Sisterfister by RoloxX September 2, 2017

Dr.sisterfister 

The man, the pope, the doc, the absolute gamer, a madlad thats has 3 monitors and a bunch of stash of anime girls, what a guy, yeah, oh but I have to warn you that he sometimes will ra-

and someone ship him with audiction, idk who, and idk when but...yes its real

Person 1: do you remember his name?, that youtuber I saw earlier in the streets?

Person 2: oh, the one that carries 2 anime body pillow?

Person 1: yea

Person 2: his name is Dr.sisterfister

Person 1: oh thanks

Dr.sisterfister by Proxley the serwofun caretaker April 13, 2020

sister fister

The act of fisting your sister. Commonly refered to as incest.

Yo this kid named Francis is a fucking sister fister.

sister fister by Quay and Justin October 29, 2003

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

sister fister by mitch aka titch September 2, 2008

Mr. Sister Fister 

Mr. Sister Fister is a middle aged man who puts his finger his sister’s vagina

That man looks like/is a Mr. Sister Fister

Mr. Sister Fister by Hepatitis A January 29, 2018