A portmanteau film is a film consisting of several unrelated, or mostly unrelated, short films. Often each one is directed by a different director. Sometimes there is a theme, such as a place (e.g. New York Stories), a person (e.g. Four Rooms), or a thing (e.g. Twenty Bucks), that is present in each story and serves to bind them together. Sometimes there is one "top-level" story, which leads into the various "sub-stories", as in Dead of Night and The Illustrated Man.
See also: