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29.
the act of pooping, in th top resiviour part some someone elses toilet.
I just gave Bills toilet an upper decker.
av Russ151 20 oktober 2006
 
30.
The act of defecating inside the water tank of a toilet.

Step 1: Go to the home of your mortal enemy. Ask to use the bathroom.

Step 2: Approach toilet and remove the water tank lid.

Step 3: Step on the sides of the toilet and squat over the water. Carefully take a massive dump. Wipe your ass and dispose of toilet paper in the trash bin.

Step 4: Place water tank lid back on the toilet.

Step 5: Escape.

What happens? With each resulting flush, it will fill the bowl with a chunky brown water. Its the gift that keeps on giving :)
Lady mere mere: Just took a massive upper decker

Bro: Are you serious? Thats messed up. You really know about upper deckers
av t-bozz 28 januari 2013
 
31.
The act of taking off the back lid of a standard toilet, hovering your anus over the opening and shooting diarrhea into the tank water. You must then wipe with TP and leave the TP in the tank. Adding red food dye to the tank is called BUD, or Bloody Upper Decker. Either with or without the dye, when the next person who uses the toilet flushes, the water that refills the bowl will be the most vile, horrific, stinky fluid known to man. Woman have been known to scream and run out of the toilet as they think their insides are coming out. Key stuff here.
"I was working a night party at that rich cunt's house. As the party was ending, I asked the beeotch if I could make a sandwich. She yelled at me in front of her guests that I will "eat with the rest of the hired staff at the end of the night!" A simple no would have been fine. For a thank you gift, I pumped a gallon of milk into my lactose intolerant ass and dropped and Upper Decker that cunt's main bathroom. Later, I Bloody Upper Decked (BUD) the upstairs daughter's fine china toilet. After that I raw dogged one of the workers and bailed, yo.'
av Dick Smartly 3 juli 2014
 
32.
Besides the common definition... A behemoth, often coiling, mass of stool that grows and grows until finally reaching above the water level of a toilet bowl. Known to be associated with binge eating. Kind of like one of those underwater volcanoes that breaks the ocean surface.
I had the munchies so bad all weekend, btw do you have a plunger I took an upper decker in your shitter and it's backed up.
av evangelicalathiest 4 april 2011
 
33.
To take a Duce in the upper part of a toilet.
Dude I just took a upperdecker in McDonnells.
av anal anilllater 29 mars 2011
 
34.
The Act of taking a shit in the Upper Tank of the toilet as a prank.
I JUST LEFT THEM A UPPER DECKER!!!
av DaddyFatSizzles 29 mars 2011
 
35.
When you have a massive deuce that must come out when your at a big party. You remove the top lid to the toilet, and release all the poo into it. When done, put the lid back on, and walk out like nothing happened.
I just put an upper decker in her toilet, HAHA!

There gonna be lookin for that upper decker for weeks,HAHA!

av boiiiiiiiiiiiiiiiiiiiiiiiiiiiie 16 januari 2006