A bag, preferably plastic, that your porn addicted roommate skeets (or jizzes) into while you're away and then reuses for 3 days and you discover when you're looking for a place to throw your apple core away and end up with your roommate's skeet all over your hand.
*He eventually throws said bag away when his family comes to visit, while they are in the room.
"Dude, is that a jizz bag in the middle of your floor? That shit is gross. WTF is wrong with you? You should just do that shit in the shower."