Um. No it isn't. It is a lack of belief in the claims that a god exists. Some atheists claim agnosticism and some claim gnosticism, but all atheism is is the lack of belief in deities. There is a difference between "I do not believe in a god" - and - "I believe there are no gods".
Both views are atheistic, because they both entail a lack of belief.
Both views are atheistic, because they both entail a lack of belief.