Sister-in-law 

The woman who doesn’t come to your wedding because she has more important things to do, yet expects you to pay for half of her wedding and will upend the entire family unless she gets her way. She is usually supported by your mother-in-law who somehow always takes her side in every possible argument.

Your sister-in-law thinks she’s entitled to you paying for half her wedding yet she has the audacity to not even come to your wedding.

Sister-in-law by Xxxxxxxxfanboyxxxxxxxxxx November 13, 2020

Sister Katie

An annoying hawt BFF girl names Katie who likes being addressed like a nun.

Girl 1: Hey look it’s sister Katie

Girl 2: Omg I knew a sister Barbra back in the 30s.
Girl 1: yea she’s weird and stupid and annoying but gorgeous.

Girl 2: I wish we could all be like sister Katie. Also have you seen her bestie?
Girl 1: Omg!! Who I thought she was lonely and had no friends. Because she acts like a nun.

Girl 2: Her name is Sister Audrey.

Girl 1: Omg I thought Sister Audrey was only a legend, but she is real and hawt.

Sister Katie by Sister69 July 16, 2021

Sister Ex 

Your ex's ex with whom you have become friends. The friendship starts out as a trauma bond, swapping stories and comparing notes on the dude's lies, cheating, and manipulative behavior, and evolves into a genuine sisterhood.

I'm getting together with my Sister Ex on his birthday to wish him a year of pain and misery.

My sister ex confirmed he was cheating on her with me when we met.

Sister Ex by ElJanel November 6, 2023

sister act 

The act of two or more sisters engaging in sexual intercourse with one or more men, usually in a threesome or an orgy.

Ah, if only Brigid had a twin, we would totally get a sister act going in my bedroom.

sister act by Robert Crumballs May 14, 2005

Sister-in-Love

When the man or woman you are dating has a sister (that you actually like) you can refer to them as a Sister-in-Love"... cuz' marriage hasn't made your relationship a law yet.

I totally just called you my "Sister-in-Love" when talking about you to a friend. I rule.

Sister-in-Love by MissVirginia March 1, 2010

Sister Sin

A four-piece "old school" metal band from Gothenburg, Sweden. They are best described as being similar to Motley Crue, except for the fact that they have a female singer. Recently released an album called "The True Sound of the Underground," which features hard-driving songs such as the title track and "Outrage."

MAN 1: "Hey man, get a load of this song from Sister Sin!"

MAN 2: "Dude, that's awesome! It's like Crue, but the guy sounds like even more of a chick than Vince Neil did."

MAN 1: "That's because it IS a chick! And she's HOT!"

Sister Sin by SmilingJack March 7, 2011

Sister whipped

When someone is hit by a nun with a bible or yard stick for swearing at church/school. Also applies to when one's biological sister whips him/her with a long object.

Person 1: God***n it!

Nun: (Slaps person 1 in the face with bible)

Person 1:Dude I got sister whipped at home
Person 2: LOL

Sister whipped by airsoftkillm March 4, 2011