Defensive Boner 

The tightening of the urethral sphincter to prevent the flow of urine. Increased blood flow to the penis constricts the urethra so you don't piss yourself in your sleep.

Sarge: "Holster that weapon private!"

Pvt P.P: "It's a defensive boner sir! I really have to pee!"

Defensive Boner by IamRob April 19, 2018