Adjective: unbelieving ,ún-bi'lee-ving
- Denying or questioning the tenets of especially a religion
"The unbelieving scientist demanded proof of the miracle";
- disbelieving, skeptical [N. Amer], sceptical [Brit, Cdn]
- Rejecting any belief in gods
"The unbelieving scientist sought empirical evidence for all claims";
- atheistic, atheistical
See also: incredulous, irreligious