When taking a shit, having someone sit on your lap aiming their anus between the first person's legs. Both people shit at the same time, creating a "double" effect and saving water in the process. For utmost efficiency, time the splashes similar to Olympic synchronized diving.
She sat on my lap while I was on the toilet so we could double deckerthat shit.
U do this to a girl u hate when ur about to climaxshove her over and the jizz in ur hand and when she tries to get up shove the jizz in her nose and run away it is called this because u humiliate her twice