upper deck verb 2noun 1forms 3 verb2 •(slang) To place a snus or nicotine pouch under the upper lip. •(slang) To perform the upper decker prank in the cistern of (a toilet).HOW DO I KNOW YOU'RE REALLY YOU AND NOT ANOTHER VOICE? YOU UPPER-DECKED THE TOILET BACK IN THE AVENGERS MANSION. I FEEL BAD ABOUT THAT, BUT I WAS MAD AT LOGAN. — 2014 noun1 •The topmost full-length deck of a ship. formsupper decked · upper decking · upper decks