Flicking your, or someone elses bum bean is when the prostate is massaged or fingers are inserted into the anus to stimulate the male G spot. This can be done to females but with less effect. This is often used by people to enhance masturbation or the sexual thrill of other people. It is an aquired taste.
Steve: i've began experimenting with Stacie, we're really getting into it.
John: ahh nice, are you going to get her to flick your bum bean?
Steve: yeah man. Flicking the bum bean makes orgasming so much more pleasurable.