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.
by iAM December 14, 2013
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Urinating and defecate in the upper portion (tank) of a toilet bowl. Coined on Bitch Slap Radio.
"Man, I hate Miami Beach so much, I'm gonna take a double decker in every toilet there.
by E.D.M. August 14, 2007
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like an upper decker except one shits on the top of the tank lid rather than in the tank
" My boss pissed me off so I snuck into his private bathroom and left him a double decker on his toilet tank."
by Vizualist February 10, 2012
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One Bro Gets a blowjob while the girl is on all fours on the ground. While this is happening, another Bro gives it to the girl from behind. Both Bro's preceed to run forwards until the girl is bent in half. Then she makes both Bro's a sandwich.
-"dude she's in the hospital!"

-"Yea i know, after we double-deckered her, she made us sandwichs, then we told her to walk to the hospital."
by Bro Bro Bro Bro Bro December 12, 2010
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While taking a duece you realize you need to puke. You cannot reposition yourself so you puke while duecing, therefore you are flowing from both floors, the double decker.
by Jon S. April 20, 2004
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When you take a shit but don't flush and then later take another shit on top of it.
I just did a wretched double decker and I think the toilet is going to overflow.
by sune3000 March 6, 2006
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