The practice of creating a volcano-style effect on the balls. Take one bottle of a carbonated beverage of your choice, and shake it up until the liquid is almost exploding out from the fizzing. Carefully remove the cap, and quickly cover the open top with the balls (try not to let much air escape). Enjoy the eruption, bro.
1. "Man, my girl's so uptight, she won't even give me a ballcano."
2. "I got a free sample of diet Pepsi, but I don't like the taste, so I gave myself a sick ballcano with that shit."