The sexual act, where two men (not necessarily gay) exchange in bobbling their penis heads in front of another then thrust forward making contact, the exchange is done over and over until one reaches climax.
steve -- "hey koji, i just got this cool doodad."
koji -- "im not sure what you mean steve, but im busy looking for my bobblynushniff so i can't talk right now."
steve -- "are you having a bubble mate?"