It gets into the realm of consciousness/self-awareness/intelligence/mind and the like. If we could transfer our mind from one brain to another, or from one brain to an artificial brain, or just patterns of electrical connections zip zapping about, then we would have many of the features of today’s woo but still be atheist because of the lack of god(s).
To get into this, you have to look not at the definition of an atheist, but rather the definition of a god.
Gods come in all sorts of shapes and sizes. Very often they have eternal life and/or knowledge/power, and when man gets above himself and attempts or attains great life or knowledge/power, the gods chop him off at the knees. Eat the fruit of the tree of life or the tree of knowledge? You’ll get booted out of the garden. Fly too high? You’ll get your wings melted causing you to crash. Get too crafty and trick a god? You’ll be rolling a heavy stone up a hill, over and over and over for eternity.
I submit that that the essence of godhood isn’t incorporeality (which in my opinion does not presently exist, but may someday exist due to technological advances in brain and cognitive biology and AI), but rather is an all too human construct that gives people something that comforts them when they grab onto it (personal belief), and provides a structure for societal organization and social control (note that prophets and religious leaders are very often into power and control over their their followers as many other people as they can, as they go about spreading their ideology as well as their geo-political, social and economic control – e.g. Christianity and Islam with their histories of violent religious conquests both between religions and within religions).
When looking at god(s) this way, you start with gods being artificial constructs created in people’s minds, rather than being real gods that really do exist. It does not matter if a god is ostensibly physical (Aphrodite), or non-physical (Spiritus Sanctus), for either way, the god is only an idea rather than something real.
Therefore as far as atheism goes, it does not matter if at some point we as humans develop the ability to have our minds leave our bodies, for that still does not make us gods or prove that gods exist.
For myself, when a person of faith says they believe in their god, I figure they are into woo and cannot even abductively prove the existence of what they believe in. If an atheist were to come up to me and say they were an atheist and they believe in ghosts, I would figure that they are into woo and cannot even abductively establish the existence of what they believe in. But that does not mean that the woo believing atheist believes in god, for believing in incorporeal beings does not mean believing that these incorporeal beings are gods.
So that brings us back to an atheist being someone who does not believe in god(s), even if that atheist happens to believe in non-corporeal minds and other such silly and unsupportable woo. My guess is that whatever it is in so many people’s brains that results in them being into woo is at the root of why many (most?) people believe in god(s) and even some atheists believe in incorporeal spirits.
TLDR: Deists believe in god(s). Belief in god(s) is belief in woo. Atheists do not believe in god(s). Some atheists believe in incorporeal spirits. Belief in incorporeal spirits is belief in woo. Not all types of belief in woo are belief in god(s).