Originated from the banana fruit in Malay, which is Pisang. The term pishang is used for when someone is really bored or rotting, as of how fast a banana skin would actually rot.
A mishap generally involving the mass consumption of alcohol and a misdirection of urine to an area other than the toilet. This usually occurs as the result of an alcoholic stupor.
Can also apply to any other misadventure in some way linked to piss.