a person who holds that the existence of the ultimate cause, as God, and the essential nature of things are unknown and unknowable, or that human knowledge is limited to experience.

a person who denies or doubts the possibility of ultimate knowledge in some area of study.

of or pertaining to agnostics or agnosticism.

asserting the uncertainty of all claims to knowledge.

noun

believer

noun

doubter , freethinker , materialist , skeptic , unbelievernotes:an agnostic is one who believes that it is impossible to know whether there is a god; an atheist is one who disbelieves or denies the existence of god or gods , empiricist , heathen , infidel , unbeliever