Gatherbration 

A celebratory event held at a restaurant or bar where everyone invited gathers and must buy their own food or drink... as opposed to a "party" where there's a host providing such fare.

Hey, Howie's turning 30 this Saturday.
Cool! Is he having a party?
Nope, he's broke. We're just hitting a bar.
Oh great, another gatherbration.

Gatherbration by Wordsmither Jim March 20, 2011

gatheration

a group of people hanging with you, at a party or just where ever!

im having a gatheration at my house

gatheration by ayaaaaaaaaaaaaa July 3, 2005

Gathernation 

A large group of people who all come together for an event.

Man I went to the "Dope" concert on Friday, it was SUCH a gathernation, I could barely move around.

Gathernation by Alicia Clark October 18, 2007