A very nice ass. Doesn't necessarily have to be huge, in fact, they're normally not. It's just a tasty looking bum-bum.

Internet persona(s) who happens to follow you and you happen to follow them back and maintain communication with and have a mutual liking for eachother whether it be friendship wise, etc. (Mutuals if more than one mutual)

Other meth addicts that come around just to smoke your bubble but never have any drugs or money of thier own.

When someone chews gum with their ass and makes a bubble thus gives it the name bubblebum