Not believing in any and all equally improbable and equally unsupported deities doesn’t really warrant a special word.  I don’t think rationality needs an interest group, and I think banding together under a proper noun would only make atheists and agnostics vulnerable to the charge of being just another religion.  It’s not a religion.  It makes no claims about the universe, and no further claims predicated on the other unproven claims, that have gone wanting for evidence for thousands of years.  Giving it a name and giving its followers an official label would only serve to lower it to the level of “competing theory” with Christianity and Islam, as if renaming modern medicine Laboratory-based Treatment Theory and calling for comparisons between it and the implicitly equally valid Guardian Angel Theory.  Being at minimum agnostic about claims of supernaturality should be the default among those having completed a basic public education; so common as to render the term “atheist” about as practical as “freeman” drawing up someone’s relevant personal characteristics.