agnostic 1 : of or relating to the belief that the existence of any ultimate reality (as God) is unknown and prob. unknowable ... syn see ATHEIST
so ... ultimate reality ... unknowable . That's my takeaway.
I have no hard copy of a dictionary right now...just my smart phone. I googled atheist definition and the search page came up with an athiest page saying it meant something like agnostic. And dictionary pages saying it means believing there is no God. And an urban dictionary that seems to say it could mean either. I only scanned first few entries and did not follow links...and it’s hard to provide links in smart phone while eating in car. But it seems consistant with my view that new athiests seem to be trying to change it. Will see if I can research its etymology properly when home...What does your tattered dictionary say in the actual atheist entry?