As an atheist, I have yet to hear another atheist say that they believe "there is no God". All the ones I have read or talked to say, "I don't believe in God". They then qualify by saying that's because they have seen no evidence or reason to believe in God and when that evidence is forthcoming they are open to changing their beliefs. That is a far cry from making a definitive statement, "there is no God".
It also irks me when believers in God try to define the belief of atheists. Beliefs, or lack thereof, are subjective and exist (or don't exist) in the minds of those who hold them. For someone else to come along and say "You believe this" because you call yourself an atheist, and that's MY definition of atheism, is the height of arrogance in my opinion.
Actually, I find it incredibly arrogant when anyone tells me what I believe. Until I share my beliefs, or lack thereof, with another, they have no way of knowing. This irked me even when I was a JW. I would stand on the street corner, and sometimes apostates or born again christians would come up to me and say YOU don't believe in Jesus Christ. Huh? I've always believed in Jesus. How arrogant is it to walk up to a complete stranger and tell them what they believe instead of listening to what they believe?