buttmate
someone who sits behind you in an office or class. They are postioned so that you seldom see their face but who shares an area but try not to touch.
Yo cuz whose your buttmate in class?
Rainbow Buttmate
The dude you go to prom with.
'Yo who you going with for prom'
-'oh, josh. We're rainbow buttmates.'
-'oh, josh. We're rainbow buttmates.'