When a guy has an erection with so much blood flow that it literally feels like his penis is about to explode. It is generally quite painful.
"The pain of grenade dick makes it much more difficult to conceal my hard-on than a typical erection."
by The Real Mister Mister August 24, 2017
When a girl gives you such bad blue balls, that the semen backs up, thereforeaking your dick and balls explode
by Ethan Vans December 21, 2016