noun
(religion) A person who does not believe in deities or gods.
(uncommon) A person who does not believe in a particular deity (but may believe in another deity).
(sometimes proscribed) A person who does not believe in any religion (not even a religion without gods); a nonreligious person.
adjective
Of or relating to atheists or atheism; atheistic.
verb
(transitive, very rare) To make someone an atheist.