Share 'is there a legal definition of a fanzine?'

Have there been any court decisions that define what is and isn't a fanzine?  I do a media fanzine.  There's a copyright Nazi who has stated he will prosecute those who try to "commercially exploit" works on a specific TV show.  Hw has also stated that he will not prosecute fanzines.   If there's no specific legal status, what would all of you mark as the border between a fanzine and a non-fanzin…