Longman Dictionary of Contemporary English
fringe theatre
noun
EXAMPLES FROM CORPUS
▪ Mime has never enjoyed a place on centre stage, it lives in the shadows of fringe theatre and the Big Top.
Wikipedia
Fringe theatre
Fringe theatre is theatre that is experimental in style or subject matter. The term comes from the Edinburgh Festival Fringe. In London, the Fringe is the term given to small scale theatres, many of them located above pubs, and the equivalent to New York's Off-Off-Broadway theatres and Europe's "free theater" groups.
In unjuried theatre festivals, all submissions are accepted, and sometimes the participating acts may be chosen by lottery, in contrast to juried festivals in which acts are selected based on their artistic qualities. Unjuried festivals (e.g., Edinburgh Festival Fringe and Adelaide Fringe Festival, and Fringe World) permit artists to perform a wide variety of works.