It’s a game. You get together with a group of people, and make up encyclopedia entries. Each entry cites other entries, some already written, some not yet written. They need not be factual; in fact, it’s probably best if they aren’t factual. This is not an exercise in erudition, it’s an exercise in imagination. At the end, you’ve got a web of 26*(number of players) entries, and presumably have had a good time.

As Michael says, it could be a lot of fun with the right group of people–rather like Balderdash on steroids, I’m thinking. But I’m having difficulty imagining how you’d pick such a group, though.