An atheist isn't agnostic. The definitions prevent that possibility. That you can't accept the definition says more about your motivations than anything. It's quite clear that you desperately don't want to accept that the definitions don't support your assertions.
Personally, I can accept when I'm wrong - but that isn't necessary or even an option in this case, because I'm not givin opinion, I'm repeating a pair of very VERY old definitions.
Let me spell it out for you using as few words as possible (from the definitions), to illustrate the incompatibility.
Atheist: disbelief
Agnostic: neither faith nor disbelief
So, if you have disbelief (atheist), you cannot be agnostic, because they have neither faith nor disbelief.
I have a feeling that you've confused agnostic with gnostic.
Good luck sorting that out. There are plenty of dictionaries online that you can use to assist you in your quest to learn the meanings of words.