Moon Sisters 

Girls who have periods at the same time.

Girl 1: Omg i have my period right now
Girl 2: Omg me too! Moon sisters <3

Moon Sisters by jtz February 21, 2013

moon sisters 

two friends who have fucked in the same room as one another

“omg we became moon sisters last night!”

moon sisters by katiemeade_10 March 24, 2022

Moon Sisters 

When you have sex in a small dorm room at the same time as your roommate

my ex and his best friend came to visit last night. his bsf was totally into my roommate so we became moon sisters over night.

Moon Sisters by shawker March 24, 2022

Sister Moon 

She is a character from the show Adventure Time and is first introduced in the mini-series "Stakes". The Moon, also called Sister Moon, is one of the 5 vampire's in the Vampire king's court.

To put it simply, she is the best vampire to ever exist in the world of monsters in all universes. Even Lady Dimitrescu's got nothing on her. Maybe. I'm not sure.

Sister moon.
"Die like pigs!"

Sister Moon by SuspiciouslySweetSubstance July 7, 2021

Moonsisters 

Girls who scissor under the full Moon

Last Friday night Cheryl and I became Moonsisters

Moonsisters by Topsy krettz April 21, 2018