I can't believe that we're really having this misunderstanding of definition... Atheistic Religion is a valid term... And since a certain someone in here just LOVES to use Webster's Dictionary, I'll break it down, using just the same...
Definition of ATHEIST
: one who believes that there is no deity
Definition of RELIGION
1a : the state of a religious <a nun in her 20th year of religion>
1b (1) : the service and worship of God or the supernatural
(2) : commitment or devotion to religious faith or observance
2: a personal set or institutionalized system of religious attitudes, beliefs, and practices
3 archaic : scrupulous conformity : conscientiousness
4: a cause, principle, or system of beliefs held to with ardor and faith
Now as you can see, I've highlighted the most important words in the definitions that will help clarify the prerequisites according to the Oh So Mighty Webster's Dictionary... Atheist is, as you can see, a lack of belief in any deity, which, while we're at it, let's show a definition of that shall we...
Definition of DEITY
1
a : the rank or essential nature of a god : divinity b capitalized : god 1, supreme being
2
: a god or goddess <the deities of ancient Greece>
3
: one exalted or revered as supremely good or powerful
So with this now in mind, let's move on to Religion... It states that it is the service and worship of a God (a deity by definition, which the word "deity" is mentioned in the definition of "Atheist") OR (key word here, which we all should know requires minimum two inputs, alternative to one another, in order to be used correctly) the supernatural... I repeat, God OR the supernatural... Therefore, only one is required to be present in order for a religion (as defined by the Almighty Webster) to be valid...
So conclusion... Athiest Religion is a valid term, which when all definitions from the Guru Webster are considered, would be a service and worship of a God or the supernatural which would require a God not be present in order to fulfill the Atheistic requirements... In short terms, a service and worship of the supernatural...