The "zorbz" is not an acronym nor is it an actual word. However it's meaning is mainly an adverb, because it shows that something is very funny but you dont know why it's funny. Or it can simply mean that something is hilarious and a little more funnier than Laugh Out Loud. But not "rolling on the floor" or "laugh my ass off" worthy.
Friend:".....and thats how the chicken crossed the road."