Main Entry: Relief Tube
Etymology Modern English by adding relief and tube.
Date: 20th Century
A tube that is used to releive the pilot of an aircraft by inserting his naughty bits in the tube and thus relieving himself. The relief tube is a great pain and embarrassment saver for said pilot.
Pilot: Hey Mac, my relief tube is too short. Last flight I had to piss myself. Now I'm not only cold, but I also feel like a fuck stick.
Mechanic: Nah, just checked it, your relief tube is factory length.