Um, what is that? (aka alien communication)
(I learned this at Kani Club, the great "Yes, and..." improv group in Tokyo.)
This game, done in pairs, challenges the listener and the speaker alike to clarify the meaning of words and phrases used. Like all games it is, as Huizinga says, "pointless but significant." The fun is in the pointless interruption and unnecessary explanation. The significance is in the verification of mutual understanding of even the simplest terms.
The flow: