step-fucker

somebody who is fucking your mom and is not your real dad. sometimes called "Step-Douche", "Step-Ass" and so on.

Alyssa: Why are you so sad?
Jess: My step-fucker just found me smoking grass.

by PhobiaOfEvertything October 29, 2015

step-mother fucker

A man who is a step lower on the social rung than a plain ol' average motherfucker.

Brian thought the was a bad mother fucker...but he's worse than he thinks...he's a step-mother fucker.

by DOTK April 1, 2010