15
A toilet prank, whereby someone defecates in the refill tank (water closet), causing each additional flush to deliver brown, poopy water into the bowl.
Jim was being such a jerk at his party, so I went upstairs to his bathroom and dropped an upper decker in his toilet.
by bodythunder November 12, 2008
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16
The act of shitting into the tank (or upper portion) of a toilet. Done as a prank, it results in at least four foul flushes (also known as a "3-F qualifier") afterwards.
"Man, I'm gonna fucking puke."

"Dude, how come?"

"Man, someone dropped an upper decker in the toilet, and the water splashed my ass and sack."

"Dude, that sucks."

"Man, I think I got a piece of corn stuck to my sack!"
by papamikedelta October 24, 2009
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17
The act of removing the lid off the back part of a toilet and pooping in it. Poop comes in the bowl over time after flushes. Usually done at big parties that have gone wrong.
The host of that party was so horrible that Andre couldn't resist pulling an upper decker before we left.
by Agenda July 12, 2005
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18
When attending a persons home of who you dislike, take a shit in the toliet tank instead of the bowl. This is by far going out of the park and into the upperdeck where it will not be known until long after you depart their house.
When your wife makes you go to her boss's party who you would like to kill, go to the bathroom and leave him an Upper Decker and you'll know who the joke is really on.
by Noah Burnett April 27, 2006
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19
When you take a crap in the tank of someones toilet instead of the bowl. Most often done to a sworn enemy or to your best friend.
I pinched one off in the upper deck. He'll have fun cleaning that out!
by Helvis September 16, 2003
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20
Step 1) Make sure nobody's around.

Step 2) Quietly open the lid of the upper-section of the victim's toilet.

Step 3) Quietly place the lid down on the floor.

Step 4) Then take a nice shit in the upper-section of the toilet without letting anybody hear you.

Step 5) Wipe your ass.

Step 6) Place the soiled toilet paper in the upper-section of the toilet or in a drawer or magazine.

Step 7) Slowly lift the lid off the floor with your fingers under it and carefully bring it over to the toilet.

Step 8) Here's the hard part; with your fingers under the lid
slowly place the lid on the toilet. No false moves or you're screwed.

Step 9) Leave and don't let anybody see you. Just bail as quickly as possible.

Step 10) Mission accomplished.
Plumber: It looks like you have feces in your toilet's tank.

Victim: It must have been an upper decker.

Plumber: Yeah right. Its already clear that you're stupid enough to shit in there!
by Mike_Litoris June 27, 2011
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21
When one takes a shit in the upper portion of the toilet. ( the tank ).
mike was really pissed that the land lord was evicting him. So he left him an upper - decker.

Jim wanted to get back at his best friend Steve for sleeping with his girlfriend, so he left him an upper - decker.
by TNT- DOUG September 27, 2006
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