Every atheist can give you a detailed description of the God in which he or she does not believe.
I was in a discussion with an atheist once, and I decided to see how deep his atheism was, so I simplified the definition to that One Universal Power, Infinite and Indescribable, which created everything.
He said, “That can’t be God.” I asked why not. “Because I could believe in that, and I don’t believe in God.”
Does a tree fall in the forest...
Very circular reasoning...and if you press them really hard about any issue about the universe’s (or life’s) origins, they inevitably circle back around to an answer along those lines.