When you need to piss really badly you start moving your legs and it looks like you are rapidly humping the air.
Person 1: You ok there mate?
Person 2: No I'm bursting for a piss.
Person 1: Stop Piss Humping. You're humiliating.
Person 2: No I'm bursting for a piss.
Person 1: Stop Piss Humping. You're humiliating.
by StephenHawking'sSearchHistory May 23, 2020
 Get the Piss Humpingmug.
Get the Piss Humpingmug. by Jamie Mosshart August 24, 2010
 Get the piss humpingmug.
Get the piss humpingmug.