Zis is when everyone in the conversation is so fucked and the conversation has degenerated to such a extent that one person will attempt to string together a bunch of words but only come out with a mumble, ie. "bluergh". Then, a second person will say, "what?" because he/she had no idea what the first person was on about. Then, the first person, in response to the second person's "what?" will then reply "what?" again. A complex sense of confusion and despair is then brought upon the group and the failed conversation.
In Ancient Greek time, the very same thing would happen and the Greek public would all mutter: "Zis", our "what?" nowadays.