piss humping

seizuring to the point of pissing yourself

I looked at a strobe light and started piss humping myself

Piss Humping

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.