Taking a dump in a flower pot because you are not in the vicinity of a water closet. Usually occurs after last call at a bar when you are walking home and get the bubble guts.
Kelton: Dude, I'm about to drop a hot load in my drawers if I don't get to a shitter soon.
Barber: There's a planter over there with some nice leaves to wipe with.
Kelton: Thanks bro, guess I'll have to take a Flower Pot Squat.