Two or more people getting together, isolating themselves and fucking each others asses off for some period of time. All in the aim of getting a lot more skilled in said activity.
When two lesbians come together one attaches a strap on to there butt and the other spreads their ass cheeks as far as they can and they bump them together
BootyBumping Redbull in fact does not give you wings. It is when your inside asshole moves to your outside asshole. It also makes your feces smell like Redbull and is violently traumatic on the human rectum.