p.o.t.m Share definition Flag poop of the month. a monthy poop in which all intestines and food is completely cleared from your tract.the runs. dude, p.o.t.m last night, i lost like 5 pounds. p.o.t.m by 4fg5d46fgs September 4, 2011 0 0 Get merch Get the p.o.t.m mug. Buy Now — $32.95 See more merch