An atheist church is a place were atheists congregate in order to discuss their disbelief of religion. However, it is here that atheists start thinking of themselves as their own deities or believe in a god "of no gods." Atheist churches are usually held in secret or in discrete locations and act as if it was a secret society.
Adam: Did you go to church yesterday?
Michael: No I'm an atheist.
Adam: No, I mean to atheist church.
Michael: Oh, yeah. We disproved Hinduism and then talked about ourselves.