Those of us who use the word atheist to describe ourselves mean to say that we are without theism. We see the burden of proof on the theist to demonstrate that the world is the way she is suggesting it is. Lacking sufficent evidence to persuade us of her claims, we don't believe them. Few if any of us take a "leap of faith" that there is no god. Certianly no more of a leap of faith than most adults do in their lack of belief in the tooth fairy, Santa Claus, or the Smurfs.