@Thomas,
Thomas, what are you reading?
Both those dictionaries you linked show that I am right.
The American Heritage Dictionary states that atheism is the
disbelief in or denial of the existence of god or gods.
Disbelieving the existence of gods is just another way of saying believing that god's don't exist. Do you think that it's not a belief if you say that you don't believe gods exist? That's just semantic babble.
If you assert something about gods, it is a belief.
Merriam Webster even goes so far as to say that atheism is the
doctrine that there are no deities.
Thank you Thomas, for asserting in this thread, beyond any doubt, that atheism is belief
about theism.