1. The act of taking consecutive shits in the same toilet without flushing. This also occurs when onsecutive hot piles are dropped in any location other than a toilet, and it is most commonly found in an outhouse at a chili cook-off.
2. Also a nickname for a short stack of chocolate chip pancakes at IHOP.
The couple was disappointed that their poostack count lowered when they moved into an apartment with two bathrooms.