Old piss is a name given to piss left in a toilet for too long and stinks up the whole bathroom. May range from dark yellow to nearly brown. Port-o-potties have this in the storage tanks along with shit. Alternatively, old piss can mean evaporated piss used in terrorist pipe bombs.
1. Dude, flush that old piss, it has stank up the whole room.

2. Put dat old piss in da pipe!! ALLAH AKBAR!!!!
by Jdeoxys November 3, 2010
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Guy in the toilet before me went for an old man piss, dirty fucker didn’t even wipe the seat
by Slazenginho November 28, 2021
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