When someone takes a dump and doesn't flush, leaving the mess for the next unsuspecting bathroom-user to deal with.
"Dude, DO NOT go in there. Someone just did the biggest shit-and-run I've ever seen."
Taking a massive, hellacious dump in someone else's bathroom (especially a stranger/acquaintance), then leaving swiftly and pretending that nothing happened.
Person 1: Hey man, why are you in such a hurry? We just got here ten minutes ago?
Person 2: Get your coat. I just took a massive shit in this dude's bathroom, and I want to get the hell out of here before he finds out it was me.
Person 1: So...shit-and-run?
Person 2: Exactly.