unbelieving
adjective
1. rejecting any belief in gods
Similar word(s): irreligious, atheistic, atheistical
2. holding that only material phenomena can be known and knowledge of spiritual matters or ultimate causes is impossible
Similar word(s): agnostic, agnostical
3. denying or questioning the tenets of especially a religion
Similar word(s): incredulous, disbelieving, sceptical, skeptical