Another definition, from Oxford Philosophy:
Simon Blackburn, ed. (2008). “atheism”. The Oxford Dictionary of Philosophy (2008 ed.). Oxford: Oxford University Press. Retrieved 2013-11-21. “Either the lack of belief that there exists a god, or the belief that there exists none. Sometimes thought itself to be more dogmatic than mere agnosticism, although atheists retort that everyone is an atheist about most gods, so they merely advance one step further.”‘
This is a little closer, I think, to the general use of “what is atheism?” in practice.
This definition is a proposition that requires first a god concept. Then an absence of belief or the belief that there is none.
Outside of atheist community circles, Tom Flynn is considered an atheist activist. He rejects any notion of “New Atheism”. back-projecting his take through time to include all atheism as being imperfect forms of his take on atheism.