n: a group of men engaged in a reciprocal, linear bufu party, each one giving *and* getting (except the front and the back man). The 'choo-choo' refers to how the synchronization required and the train of people would make this look like an old steam engine running.
Also, and more commonly, denoting an event which boils down to effectively a lot of mutual reamage or time wasting; good or bad connotations possible.
Person1: Did you go to the project lessons-learned meeting?
Person2: Naw, man, I figured I'd just get the meeting minutes emailed to me, and miss the bufu choo-choo that meeting must have been.