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1.
A game related to beer pong that was started in Port Washington, Long Island and is rapidly spreading across Long Island and the New York metro area.

The set up of the game is a standard 10 cup beer bong triangular formation. However the front cup is an either hard/dense plastic cup (regular party cups will not do) or a ceramic cup. It is important that the front cup is the color green. It is also important that the green front cup is no less than 2.5 inches taller than the rest of the cups. The rest of the cups can be regular plastic party cups.

The basic difference between greencup and standard beer pong is that when the team makes it in the greencup they get to make a rule that the other team must follow for 5 turns. Despite the similarities, it should be noted that green cup is not just a variation of beer pong, but its own individual game that requires unique creativity, strategy, and concentration.
Person 1- Johanna gave Carolyn a lap dance while shooting
Person 2- Classic greencup
by greencup21 January 18, 2012
 
2.
The green cup is the cup used to expel your body fluids because you're too lazy to dispose of them else where, this could be urine, semen, female ejaculations, spit, etc.
gup green cup

(guy1)- "yo can i get a drink?"
(guy2)- "yeah, just dont use the green cup"
(guy1)-"why?"
(guy2)- "because i nut and piss in it"
by nightscloud2 April 04, 2009