I've had this idea in my head for a while. 

Imagine a game where the players picked descriptive qualities, but before the game started the whole group jammed on what descriptive qualities were available?  For example, it would be up to the group if Wizard and Ninja were sufficient, or whether there should be Conjurers, Pyromancers, Killers, and Sneaks.  The GM would be in on this too; there the GM is putting in things that will be used for NPCs and Villains, again everybody getting on the same page.  So the GM might say "Brute" and "Tainted" and players could say "let's break that down to Meaty, Savage, Corrupt and Cancerous."

Sort of like a thematic agreement before everything begins.

Are there any games that do this, or procedures that could handle this kind of initial jam session?

Universalis sets up every new game/campaign pretty much just like you describe, with folks bidding coins to assert Facts about the setting and general situations.

David

I tried universalis once but it just didn't take off.  The whole (4 hour) session was spent saying "what phase are we in right now?" and "can we talk now?"

Is it available in .pdf?  I hate ordering dead trees when I'm paying for ideas.