Plopping Bunghole
When one person sucks anothers penis until he cums then spits the cum into his/hers asshole, then the two people go bunghole to bunghole and farts the cum into each others assholes, thus making a plopping sound as thr cum bubbles from asshole to asshole
Dude, last night Jenny and I did the plopping bunghole, It did take while to clean all the cum out of our assholes.