This would be problematic for the atheist.
See [youtube]mNxbXQecm2I[/youtube]
this video. I have to say WLC has a point.
To the OP. Here is my definition.
Atheism is a belief that all organized religions are wrong. Why? There is no evidence for any of the claims that organized religions make. So, atheism needs the existence of theism so that atheism can be a philosophical position.
Now that I have defined atheism to be a belief, I should shoulder the Burden of Proof. However, I need to do that only if I want to convince someone of atheism. I dont. Without arguing for my position, I am well within my right to question theists.