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 decker that shit.
To leave an Upper Decker in the toilet tank, and to leave a Floater in the bowl. This can either be a two-man job, or performed by a single person who breaks his payload into two segments. The result is that the water in the bowl will be brown, and the water that comes from the tank during a flush will also be brown.
An upper decker wasn't enough for that place, so for good measure I left a double decker.
When you take a deuce in the upper tank of the toilet. Leaving the owners to believe the toilet is broken, since the water comes out brown and pieces of fieces. This continues until someone either scoops it out of the upper tank or it dissolves.
Usually happens at mad crazy house parties or when someone mad dogs another person and allows them to use their bathroom.
When you sit on your homie’s shoulders with your nuts in his face and shit through the space in between his legs.
Yo, me and devon dropped a steaming double decker earlier in the church bathroom!
Taking a crap in the upper part of a toilet, then in the bowl, forcing the owner to flush in dismay, and in stench.
Oh man, I freakin double deckered that toilet, sucks for them!
The act of taking a shit while another is sitting on your lap and shitting simultaneously between your legs.
Perry and Carl both had to shit but only one toilet was available so they performed a double decker.
When someone takes a dump with someone on their lap
I took a double decker with Sally today