The act of male masterbation, in which the semen flows like goo out of the tip, thus making it appear as if a volcano erupted onto ones hand. Can also be used as an insult.
"Man, I was tugging one out last night when to my demise, it ended in a hand-cano!"
Insult: " Oh man that kid Tyler? He can go hand-cano himself he's a real bitch."