I think a prophet simply means some who predicts the future accurately (or inaccurately) : "seer, soothsayer, fortune teller, clairvoyant, diviner; oracle, augur, sibyl"
For all we know, David Icke, Alex Jones, Nostradamus, and authors of works such as
http://www.sacred-texts.com/cla/sib/index.htmBEGINNING with the generation first
Of mortal men down to the very last
I'll prophesy each thing: what erst has been,
And what is now, and what shall yet befall
5 The world through the impiety of men.
First now God urges on me to relate
Truly how into being came the world.
And thou, shrewd mortal, prudently make known,
Lest ever thou should'st my commands neglect,
10 The King most high, who brought into existence
The whole world, saying, "Let there be," and there was.
For he the earth established, placing it
Round about Tartarus, and he himself
are all divinely inspired? Or at least they tried to reach the divine. Prophets like Mani, Zoroaster, and many others...
Nietzsche? He authored "Thus spake Zarathustra". Obviously he was intending to prophesize. Later on he claimed to be God and wanted to give warnings to the world, and "lost his mind".
Sure. Science fiction authors may also be classified as predictors of the future. Atheist and secular prophets!