The word "Mythic" is sometimes used in Biblical scholarship. It's usage can be disturbing for those of us who believe the Bible reveals the truth of God. I came across the following definition while searching for a biography of Luke T. Johnson. It's from the "Ancient Evangelical Future" Blog. It's the best most succinct definition of mythic in this sense of the word that I've found.
Note: Mythic here does not mean “fictitious,” but refers instead to the language that transcends the natural world and provides an explanatory framework for why things are the way they are.Link:
http://ancientevangelicalfuture.blogspot.com/2008/02/christology-luke-timothy-johnson-on.html