A shitty poster...a pisster.

Coined by a Brit who couldn't say poster...

when you're hungover as shit after a spending a night drunk as a skunk

Two or more people who have established a ritual bond by urinating in the same toilet at the same time. There is no male form of the word, and therefore all people who perform this ritual are "Pissters" with each other, regardless of gender.

To make more pissed off.

Sisters that piss is the same toilet bowl before flushing.