BlueMooner: 1) "disbelief or lack of belief in the existence of God or gods."
http://www.oxforddictionaries.com/definition/american_english/atheism Right, the belief in a negative. As I stated. If you lack belief in a God or gods, you implicitly believe there is no God or gods, since they are mutually exclusive.
BlueMooner: You can also read About's definition of atheism here:
http://atheism.about.com/od/Atheist-Dictionary/g/Definition-Atheism.htm 3)
Wikipedia says:
"Atheism is, in a broad sense, the rejection of belief in the existence of deities.[1][2] In a narrower sense, atheism is specifically the position that there are no deities.[3][4][5] Most inclusively, atheism is the absence of belief that any deities exist.[4][5][6][7] Atheism is contrasted with theism,[8][9] which in its most general form is the belief that at least one deity exists.[9][10]"
Same goes for the broad definition here.
BlueMooner: I agree with footnote 4 from there, which says:
"Harvey, Van A. "Agnosticism and Atheism", in Flynn 2007, p. 35: "The terms ATHEISM and AGNOSTICISM lend themselves to two different definitions. The first takes the privative a both before the Greek theos (divinity) and gnosis (to know) to mean that atheism is simply the absence of belief in the gods and agnosticism is simply lack of knowledge of some specified subject matter. The second definition takes atheism to mean the explicit denial of the existence of gods and agnosticism as the position of someone who, because the existence of gods is unknowable, suspends judgment regarding them ... The first is the more inclusive and recognizes only two alternatives: Either one believes in the gods or one does not. Consequently, there is no third alternative, as those who call themselves agnostics sometimes claim. Insofar as they lack belief, they are really atheists. Moreover, since absence of belief is the cognitive position in which everyone is born, the burden of proof falls on those who advocate religious belief. The proponents of the second definition, by contrast, regard the first definition as too broad because it includes uninformed children along with aggressive and explicit atheists. Consequently, it is unlikely that the public will adopt it." "
This is an opinion. I am sure his work is a compelling read (no sarcasm intended), but the way one man views certain words does not change their definitions. No matter how educated the man is, nor how much anyone would wish his opinions to be valid.
BlueMooner: 4) Lastly, this non-dictionary link (a-dictionary?) shares my views, with the benefit of a little graph as well:
http://clearbluereason.org/649/what-is-an-atheist/
The link won't work for me. Regardless, that site is not a dictionary that I have heard of before. I, personally, would take definitions from that site with a grain of salt.
EDIT:
The link finally worked. Yeah, as I suspected, the site you linked can hardly be seen as an impartial source. :)