Buddhism is techically an atheist religion, if you go by the less-usual interpretation of atheism as meaning “without belief in any deity.” But it’s not necessarily compatible with the materialist interpretation of atheism. Buddhism dates back to Iron Age India. There is a lot of woo-woo in there.
It’s a tad bit annoying to me to see scientifically-minded atheists turning their backs on their own culture to appropriate a pastiche of someone else’s, but that’s the world we live in today.
But to answer your question, atheist is just a word, not even a very semantically rigorous one. Atheist beliefs are almost as varied as Buddhist beliefs, would probably be even more if there could be hundreds of millions of atheists.
I’ll just say that if you’re going to find meaning in Eastern spirituality, maybe find a different label for yourself.