Crosmando: Really now? While that might be the 'literal' meaning, I think you'll find many (most?) atheists associate not believing in god/s with not believing in anything superstitious/supernatural, such as ghosts, spirits, etc.
Most atheists could like the color green. That's doesn't make green something that defines an atheist. Of course they would reject the common notions of spirits and magic proposed by its supporters, because "supernatural" is a term coined specifically to create the impression of something beyond our understanding and our universe.
That does not exist for atheists by definition. To an atheist, that would be something that humans can understand but have not yet discovered the science behind. It would still be natural, not supernatural. And if there was no way something could be explained then there would be no reason to assume that it actually happened or could happen.
And on that note, Chris Angel would have been considered a god in ancient societies. As would a highly durable, bipedal squid-man. Our standards today have risen from that to "must be unfathomable, intangible, invisible, and have every superpower" to counter our increased reasoning abilities. But squid-man, with his super tentacle strength and pleasant manners living in our unexplored ocean, that would be more sensible. ^^