In a basic form, just telling everyone involved in the situation or just the situation itself to Piss off! Showing your lack of interest or care for it any longer.
Originated from the bananafruit 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.
Hey, I'm feeling really pishang at the moment, I think I need to start finding a new hobby.