Is atheism a belief?

[Belacqua]

What type of scientific evidence we would need would depend on how we are defining god, which is the problem. 

Right, you take it as axiomatic that evidence is only scientific evidence. This is a strong belief that you have. 

I don't think you were trying to avoid answering the question. I think you didn't understand my question, due to the fact that you consider the answer self-evident. 

It's certainly true that if we begin with the axiom that only scientific evidence is good, then there is no evidence for the existence of god. 

As for how we are defining god, there are many definitions given over the millennia. I offered one, and you claimed that I had said nothing. That seemed odd to me. There are definitions. Again, you may be taking it as axiomatic that they are not good definitions. Or you may be unaware of them. 

You said, and I quote...

Religious people may also include revelation, authority, tradition, the logic of natural theology, and the logic of metaphysics.

Please read that sentence carefully. It says that religious people hold those things to be good evidence. It does not say that I agree with them. 

The point I am making is that YOU have a belief about what constitutes good evidence. You apparently have reasons for believing this. (Unless you want to assert that you believe it for no reason.) 

So you are making a positive claim. You are claiming that only one type of evidence is good. And if you are making a positive claim, this is something which you need to defend to people who disagree with you. 
Therefore, a key element on which your lack of belief in god rests is a positive assertion requiring defense. 

So it may be true that your atheism is only a lack, but it is a lack resting in a web of beliefs concerning what constitutes good evidence. And if that web of beliefs were to go away, your atheism might well go with it.