Believers, put yourself in my place.

[Whateverist]

Perhaps, what is wrong too with defining atheism as lack of belief in God is to not define anything at all. For all -ism holds on to some affirmation and not merely describing some lack-ness. This is the first time that a term with -ism is defined with lacking. Are there any other definition which have defined the way new definition of atheism is defined?

Do you believe in throggs?

Simply because something is undefined does not necessitate that thing's existence.

And if you don't believe in them because you don't really know what it is but suspect it is something silly, does that mean you positively believe throggs do not exist?  I suspect like us you prefer to leave open the possibility of your being mistaken even as your initial triage leads you to deny belief in them.