backbust Share definition Flag To blow one's orgasmic load of either vaginal or penile secretions onto an unsuspecting strangers back. Matt: DUDE WHAT THE FUCK IS THAT?! Nadsack: u just got backbusted! biotch! backbust by cockjuggling thundercunt March 23, 2009 0 0 Get merch Get the backbust mug. Buy Now — $32.95 See more merch