An excellent definition of atheism provided by online persona AdamHazzard.
“As an atheist, I believe gods exist. Lots of them.
In fact I believe two classes of gods exist: narrative and hypothetical.
Narrative gods are marvelous beings with unprecedented, extraordinary powers or origins whose acts are described in legends, folk tales, mythologies, and religious narratives around the world. Examples of narrative gods include Zeus, Vishnu, Nyame, Yahweh, Baal, and countless others.
Hypothetical gods are the gods of philosophy: they exist as hypotheses or free-floating definitions. They are distinct from narrative gods, though some belief systems may conflate a narrative god with a hypothetical god.
Theists agree that gods exist in this sense, but make a further claim: One or more of these gods has an objective existence outside of narrative or hypothesis.
I reject that claim as unevidenced: therefore I am an atheist.” –AdamHazzard