GBTT 

It is a slang term meaning gang bang.

After the homecoming dance, we should definitely GBTT.

GBTT by BrickTamland September 20, 2008

GBTTK 

Short for "Get back to the Kitchen".

<Becky> i'm a girl
<Tom> girls don't exist on the Internet
<Bill> tits or gbttk!

GBTTK by LaClown May 1, 2009