Someone who ruins a party by getting totally wasted and shits on the floor, the couch, his friend's polo, the wall, and many other places. As well as shitting all over the place, a Party Pooper can sometimes also throw up underneath a dog bowl, piss on the kitchen floor, or on someone's shoes. The Party Pooper usually awakens the next morning covered in his own shit, vomit, and piss. The Party Pooper flees the party house in a state of confusion, leaving his disgruntled friends to clean up his disgusting mess.
A classic example of a Party Pooper is Tyler Price, who did everything that is described in the definition.
Before ejaculating on your partners face, shove a handful of confetti in your anus. After ejaculating quickly turn around and fart out the confetti on your partners face causing it to adhere to the semen. Often followed up by the male yelling "Surprise!"
I had leftover confetti in my house so what else would I do? I gave her a partypooper of course.