Lazy Girlfriend 

When a male in a relationship ejaculates onto his female partners butt. This can be done while he is rubbing his penis in between her butt cheeks, or masturbating. If the girlfriend is too tired, not motivated, or busy with something else, she may let her male partner do this so she doesn't have to participate, yet her boy friend will be able to ejaculate.

Jenny was tired after a long day at school, so she gave her boy friend a lazy girlfriend

Stephanie was busy online, so her boyfriend Connor asked her politely for a lazy girlfriend

Lazy Girlfriend by expand-dong420 September 20, 2015

Lazy Girlfriend 

Beating off onto the ass of a lazy/sleeping sexual partner, usually done when drunk or extremely horny.

Bob: Yo man, you get any action last night?
Todd: Nah, Suzan was "too tired" so I just pulled down the back of her pants and gave her a lazy girlfriend.

Lazy Girlfriend by DKNJ420 December 24, 2008