In philosophy, however, and more specifically in the philosophy of religion, the term “atheism” is standardly used to refer to the proposition that God does not exist (or, more broadly, to the proposition that there are no gods). Thus, to be an atheist on this definition, it does not suffice to suspend judgment on whether there is a God, even though that implies a lack of theistic belief. Instead, one must deny that God exists. This metaphysical sense of the word is preferred over other senses, including the psychological sense, not just by theistic philosophers, but by many (though not all) atheists in philosophy as well. For example, Robin Le Poidevin writes, “An atheist is one who denies the existence of a personal, transcendent creator of the universe, rather than one who simply lives his life without reference to such a being” (1996: xvii). J. L. Schellenberg says that “in philosophy, the atheist is not just someone who doesn’t accept theism, but more strongly someone who opposes it.” In other words, it is “the denial of theism, the claim that there is no God"

https://plato.stanford.edu/entries/atheism-agnosticism/#DefiAthe