ok...i still see those at 2 totally distinct different things.
atheist = definitely doesn't believe god exists. no chance to believe that god exists.
agnostic = you're not sure if god exists or not. there is a chance that you would believe.
agnostic is not a term you can use on its own. People have misused the word for generations, and I just don't get it.
Agnostic = without knowledge. Period. It doesn't imply knowledge of what. It's a type of certainty, and in truth for the longest time it, when used to describe certainty and knowledge, is connected to spirituality. The opposite, gnostic, has been used by many in the same light.
Most religious people, if they are halfway sane, should identify as "Agnostic Christian", or whatever religion.
When it is attached to something, it means you don't have 100% certain knowledge of what it is you believe. You may have a very strong belief, but you feel there isn't anything concrete, no accurate physical proof.
Same goes for atheists.
They, if they are sane, will identify as Agnostic Atheist. That means they don't believe in god, but they don't see anything right now offering certain proof alluding to god's existence, or lack of existence. They may be a firm non-believer, like myself, but acknowledge the fact that, while it makes sense to us for a deity to not be real, there is no 100% certain proof.
These are the kinds of atheists that, if a god ever came down in front of them, and said "Son, I am disappointed. I am God, why do you not believe in me?" and then does some fancy godly tricks to prove he is god, well... to put it simply, we'd accept proof of existence and acknowledge the deity. It would actually be a funny jump, going from Agnostic Atheist to Gnostic Theist.
If someone identifies as Gnostic Atheist, well... they're just absolute assholes who too deserve to be burned. I mean seriously, I think this god stuff is ridiculous and one big fairy tale, but to claim you have 100% certain proof of something NOT existing... that's just pushing the boundary.
And while not 100% true, basically these are the types of people who, even facing down a deity and witnessing proof, they'd still deny reality.
If someone is, by the incorrect term "Agnostic", I'd argue the real identifier would be Agnostic Theist. Not attached to a religion or claims of what type of God or its motives, but rather... they just believe, even if ever so slightly, that there might be a god out there. But they also don't know and don't think there is proof one way or the other.
They could use Deism or Monotheism as titles next to agnostic to further imply what their non-religious root belief is like.