Atheist: a person who denies or disbelieves the existence of a supreme being or beings. Sorry but thats what it is, and if thats how you feel, you are an atheist. A murderer might not think of himself as one, but thats what he is when he murdered someone.
Now take myself for example, I dont consider myself an atheist, and probably not a christian either or anything else. See, you flat out do not believe in deities or gods or any kind of supreme being, and that makes you an atheist, where I say no one knows, and that puts me nowhere I guess. I see it this way: there may be a God, there might not be a god, and it could be a christian, jewish, hindu, muslim or any god, but none of us here on earth know the truth, and if someone tells me that they know the truth, I call them straight up liars.