Atheism is the rejection of ALL religion and ALL beliefs in ANY god of ANY type.
it means "lack of religious belief" so how the FUCK is that a religion?
Not to nitpick but this is not exactly the case. Literally, "atheism" is derived from the Latin word "theismus" (meaning the belief in the existence of at least one deity) and the Latin prefix "a" (which means "without"). Therefore, the specific definition of the English word "atheism" means "without the belief in the existence of at least one deity". It makes no direct reference to religion in general.
I make this important point since many people refer to Buddhism as an "atheistic" religion since it neither acknowledges nor denies the existence of a deity or deities (I personally do not believe that necessarily makes it atheistic at all). Although certain Buddhist sects choose to believe in a deity or even multiple deities (especially Nepalese & Tibetan), virtually all modern versions of Buddhism do not recognize the earth or universe as being either created or ruled by any sort of god or gods. The question is simply not an integral one to the central theme of Buddhism.
Damn it....I said I was going to stay out of this discussion!