When a prisoner throws some kind of bodily fluid on a guard. They could throw fecal matter, pee, sperm, or blood on someone. This is called "gassing" someone.
noun: ALSO Someone's trying to tell you they have to fart. "They have gas."
Prisoner: "I'm going to help you"
Guard: "and just how is that? How?"
Prisoner: "Prisoner 8672 is going to try and gas you tonight."
Guard: "Thanks for the tip. I'll watch out through the vents where they usually throw it."
First heard and proliferated by the sad and loney at the www.harmonycentral.com Guitar Effects forum.