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.
a squat toilet; a low, ground-level bathroom fixture used for defecation and urination. More common in Eastern cultures, particularly public restrooms. See Wikipedia article for "squat toilet"