A primed cannon is when a man's penis is erect and sticking out of the fly/waistband of his underwear/pants, but his balls are not. Can almost be considered the opposite of pitching a tent.

The primed cannon sticks out of the ship, but the balls and seamen are safely stowed inside.
"My dad walked in on me in the bathroom this morning."

"Agh, gross."

"What's even worse is he didn't seem to notice his morning wood was a primed cannon..."
by Mr. Whim September 9, 2009
Get the primed cannon mug.