fanon

noun

1. A vestment reserved only for the Pope for use during a pontifical Mass.

2. Part of a bishop's mitre. They are the tabs extending down from the mitre, often with a cross near the end of each. See lappet.

3. A maniple.

4. (informal, fandom slang) Elements introduced by fans which are not in the official canon of a fictional world but are widely believed to be or treated as if canonical.