Atheism is the disbelief of a supreme ruler over looking everyone (i.e. God) but the belief of Heaven and Hell is still there... Atheism isn't a supporter of Satan which many people say... That would be Satanism. There are Atheist Church that still strive for a good life and to be kind to one an another so they can visit there innocent grandmothers and grandfathers that died in Florida in Heaven...
Agnostic people aren't religious at all... They're not people who don't want to admit to being an Atheist... They're just people who couldn't give a rats ass about religion and don't believe in all the written up crap in a book... They don't believe that if they save a bunny from falling off race car while eating a bag of puff Cheeto's will give them an admit-one ticket to heaven.
No, no, no, no, no, no, no, no, no, no, no, no, no, no, no.
I really ought to put a few more no's there just to stress how incorrect this statement is.
its acctually far more simple. Theism is simply a beleif in god/gods. Atheism is the oppsite. Atheism is as you posted 1. the doctrine or belief that there is no God.
Simply put
Atheists don't beleive in a god full stop, there is no further certification for atheism required. I don't beleive there is a god therefore I am an Atheist, I have no religious practices what so ever either.
I can't see where you get the idea that atheists somehow don't beleive in god but do believe in heaven? Atheists simply don't beleive in god, if you don't beleive in god then that makes you atheistic, unless you are not sure whether you believe in god or not, in which case you are considerd agnostic. Quite where the beleif in heaven or hell comes into it I have no idea.
I have never heard of an atheist church before (which is where I am assuming what you thought being an atheist meant ) seems quite an unusual concept and I am fairly sure most atheists aren't religious but yes i would agree members of this curch are religious, even if they don't beleive in god.
So its a shame to hear that you find people who argue Atheism isn't a religion an annoying social habbit because it turns out they where right, Atheism isnt a religion although its not impossible for atheists to be religious either.
For the record, I do not believe there is a god, I am therefore Atheist, I could however technically be considered agnostic.