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1.
A term used in New Orleans to refer to the plastic cups given by bars to their patrons so that they might take drinks off of the premises, as in to-go drinks or at closing time.
"It's closing time, guys. Want your beer in a go-cup?"
by eViL pOp TaRt February 10, 2006
 
2.
A plastic cup like vessel used for urination when access to a toilet is impossible.

Can be any cup, though there are cups sold specifically for this purpose.
Dave peed in his Big Gulp and threw it out the car window. He needed a go-cup badly and it sufficed.

Gimme a go-cup dude, Im about to explode.
by Immortal Yawn October 07, 2011
 
3.
a cup used to hold any beverage that one may take with them while they are out and about/while they are on the go
"Mom gave her child a go-cup in case her child got thirsty in the car"

"We all had our go-cups when we went hiking the new trail"
by DazzDeLaMorte March 14, 2007