How do most people understand the word "Myth"?

I like the definition that Joseph Campbell refers to, that a myth is a story with explanatory power. With that understanding, there's no connotation whether the story accurately describes an historical fact or not. It is the opposite of the sense of the use of the word by the guys on "Myth Busters" who used myth as synonomous with fiction or misconception. I don't think that's strictly what myth means at all, but I suppose words mean what the majority of people believe they mean, at least in English in America, where we don't have an official Academy to decide.