fister sister 

1. a female who likes to engage in the ancient art of fisting with other women.

2. the act of fisting your female sibling.

3. an order of nuns devoted to fisting

1. watch out for that chick, i hear she's a fister sister

2. A: i often like to fister sister
B: you mean, fist a sister?
A: same thing dickhead

3. she is a sister of the fister religion.

fister sister by 60 2nd squire January 5, 2009

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

sister fister

Anyone who has shoved their hand into a friend's sister's cunt

1) WOW I PULLED THE SISTER FISTER ON STEPH
2) I pulled the sister fister on blakes sister

sister fister by Zane April 4, 2003

ur sister fister 

Stronged then any of the ur mom gay insults

Person 1 : ur mom gay

Person 2 : ur dad lesbian

Person 3 : Ur granny Tranny

You : ur sister fister

*world melts and universe explodes*

ur sister fister by Zygno April 4, 2018

sister fister

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

Yo this kid named Nicholas O. is a fucking sister fister!!

sister fister by Dankolas O. January 25, 2016