(noun)A young man who is boinkin’ his stepsister.
(verb) to pound your stepsister into the mattress.
(verb) to fill every orifice of a stepsister at every available occasion.
“Dude, I’m beat. I pulled off a 4 hour stepsister-sticker with Jasmin last night.”
“Man, I’d like to ask her out, but that big bastard over there is her stepsister-sticker.