people who shit or "poop" themselves during school, parties or family outings. often large pale teenagers who are sexually insecure and rely on the warm feeling of shit on their bum cheeks to make them sexually arroused
Someone who makes a game of hiding their turds in places hard to find, in closets, under beds, in cabinets or drawers etc. This is so the smell of shit fills the room but no one knows where it is coming from and eventually have to hunt down the shit and clean it up while the poopster watches all this and tries to hide his laughter.
"You hear the Poopster struck again? 5th time this semester. This time it was under the back seat of the principal's car. Poopster got some skills."
Variation of the word "puppy". "Puppy" becomes "poopy", and therefore "poopy" becomes "poopster" by the nature of human beings to add a -ster at the end of everything.