Someone who just doesn't care whether God exists or not and realizes that such a fact won't effect their life anyway, comes from the word 'apathy' meaning "absence of emotion" and 'theism' meaning "belief in God"
Susan: "Are you an Atheist? Agnostic? Theist? What???"
Ryan: "None of the above, I really just don't give a shit"
Susan: "So what are you then?"
Ryan: "An apatheist because, like I said, I just don't give a shit and wonder why anyone else does too"