A sexual act in which a woman, during her period, inserts a ping pong ball into her vagina. She then, using muscle contractions, pops the ball out, hopefully causing it to fly some distance.
"Dude, my grandma can rusty cannonball farther than you can throw a football"
"You'll never believe it, but my girlfriend almost took my eye out with a rusty cannonball last night"
Buy a
rusty cannonball
mug!
