Secularism is the principle of seeking to conduct human affairs based on naturalistic considerations, uninvolved with religion. It is most commonly thought of as the separation of religion from civil affairs and the state and may be broadened to a similar position seeking to remove or to minimize the role of religion in any public sphere.

That's the introduction from Wikipedia, which matches my understanding of the definition. It's not synonymous with atheism. However, given its stated mission of minimizing religion, it seems like it would be relatively unconcerned if atheism were to be treated more favorably.