Choco Busting is when you masturbate while trying to take a shit. Essentially something that nobody really does but you don't know that of course. It is also a tactic someone does when constipated to try and take a shit and afterwards if successful you bust a nut on your human chocolate. This can also be done when you're not having problems taking a dump but can still go ahead and masturbate during the process.
Guy: Hey what's taking so long in there?
Guy 2: I'm taking a dump but it got stuck
Guy: Have you tried choco busting?