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.
by 60 2nd squire January 5, 2009
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The act of fisting your sister. Commonly refered to as incest.
Yo this kid named Francis is a fucking sister fister.
by Quay and Justin October 30, 2003
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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
by mitch aka titch June 11, 2006
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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
by Zane April 5, 2003
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The act of fisting your sister. Commonly refered to as incest.
Yo this kid named Nicholas O. is a fucking sister fister!!
by Dankolas O. November 19, 2015
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