Atheism runs a long gamut of epistemic positions. Rare are those who hold a fast believe that God doesn't exist (by any definition). The default atheist position is that we don't know and the standards we use to test or hold positions of belief regarding other things we don't know about (from the nature of ball lightning to the possibility of cyptids or -- to cite some common thought experiments -- invisible pink unicorns or fairies at the bottom of the garden) can also be applied to spiritual and supernatural elements like human souls, Hell and God.

This may sound agnostic, and as per other identities, we are each free to choose the identity name we prefer. But what we have established from centuries and centuries of observation stacks pretty heavily against the supernatural assertions of popular religious faiths. We can expect that Jesus didn't likely actually rise from the dead, just as much as we can expect neither Zeus nor Thor nor Adonai command the thunderbolts (rather they seem to hold fast to electrostatic mechanics, and replaceable grounded lightning rods do a lot of heavy lifting redirecting lighting away from the big iron bells in steeples and bell towers... or doing too much damage to Christ the Redeemer in Rio De Janero.

Classical agnosticism comes from a Christian tradition, asserting we don't know which interpretation of scripture is right, or if there's another explanation, but that is part of the test of faith. In the modern day as Dawkins noted in his 2002 Call to Arms TED lecture, agnostic is atheism lite, not willing to admit that God as He is (They are) understood to be by most folk, is not just improbable, but infinitesimally probable based on our knowledge of the mechanics of the physical world...and on the conspicuous silence of the supernatural (We checked! A lot!).

So a safe differentiation might look like this:

Agnostic: I believe there's a 10% chance Jesus was resurrected by divine miracle.

Atheist: I believe there's a non-zero but insignificant chance Jesus was resurrected by divine miracle

I'm a naturalist, which is to say, I haven't been able to find any evidence for supernatural events, and regard them much the way I would the notion there are invisible pink unicorns that live in Angeles Crest Forest. This is not to say science has figured out everything (we still struggle to make sense of ball lightning, though it's definitely a thing in Missouri) but much of what we figured out points away from all the other common models.

I can speculate there is a God (or a pantheon of gods) but this gets classified with a range of other possibilities, such as the simulation hypothesis, or Azathoth's dream. (We may all be figments of Azathoth's imagination, but if so, Azathoth has provided for a robust dream-scape that is extremely consistent with its physical mechanics, even when we try to break reality.) Any of these could be true, but for sake of day-to-day living, our world appears consistently to behave as material, and nothing else.