Pisster Sister 

When there is more than one sister, whoever is the pissest is the Pisster Sister, and the less pisster must therefore look after the Pisster Sister.

Sister 1: I'm SOOO wrecked!
Sister 2: Not as wrecked as me!
Sister 1: I SOOO am!
Sister 2: Okay.
Sister 1: Okay?
Sister 2: Okay.
Sister 1: Okay!
Sister 2: So, you're the pisster sister?
Sister 1: I'm th...(falls down, unconscious).
Sister 2: Yeah, ye'are (Sister 1 then proceeds to carry Sister 1 home).

Pisster Sister by Sinead April 22, 2005

Sister from another pisser 

The female version of brother from another mother

a girl: hello my sister from another pisser

Sister from another pisser by dinky Deli Food October 15, 2011