The act of participating in an extremely fun activity consisting of 3 or more people. Usually, a couple will be involved, in which the GIRLFRIEND to THE COUPLE does not agree with GROUP PARTY THING, but still decides to go along with her fellow mates desires.
Dude: Hey...would you like to go on a cruise????

Dudette: YES...I'VE ALWALYS WANTED TO GO ON A CRUISE!!!!!!!!!

Dude: Yeah...well let's make it a GROUP PARTY THING!

Dudette: Huh...Group...PARTY THING?!?!?

Dude: Yeah

Dudette: Ok...sounds cool, I'm down for anything...
by YUM7227 August 19, 2008
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