I think a cult film is any film that either has a rabid following (and this includes mainstream films like "The Wizard of Oz", "Star Wars", "The Lord of the Rings", etc.) or any film which has been either a critical or commercial misfire that has a devout following ("Night of the Living Dead" "The Rocky Horror Picture Show", "Donnie Darko", etc.). The films can come from essentially any country or culture, though they may or may not exemplify the typical films of that country or culture. Seeing as how I'm rambling, I'll attempt to sum up. A cult film, a cult book, a cult musical artists or band, is basically just an aspect of pop culture that spawns its own sub culture.