|A story each installment of which is by a different author. The usual type consists of alternate segments of half a page or so. In subzines, however, success has attended longer works, each chapter of which was by a different author. There were some by Pros in the old Fantasy Magazine, including one which for novelty's sake was written backwards -- last installment first, that is.
The gimmick, of course, is to leave things in such a mess at the end of the installment that it takes brainwork on the part of the succeeding author to solve the problem and get on with the story. Some of the more famous round robins have been "If I Werewolf" in Spaceways, "The Challenge from Beyond" (in two versions, one by stf authors and one by weirdists) in Fantasy Magazine, and the "Great Stf Broadcast" / "Stf Broadcasts Again" pair in Spacewarp. More recently Stellar offered "The Death of Science-Fiction" in which US Victory in World War III spawned a Gestapo-like Sedition Control Authority. Various fans represented themselves & friends fighting it melodramatically.