couch condom
Anything such as a sheet, blanket, sleeping bag, trash bag, etc., which might prevent one from contact with a soiled couch, especially on upholstery soiled with sweat, sex juices or butt smudges. Much in the same way a pillow case or a t-shirt can protect one from a filthy pillow.
"Both Cyka's aunt and Booby have had real nasty sex right there. You'll probably want to throw down a couch condom before you rest your dizzy head there."