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. Synonyms: disbeliever, nonbeliever, unbeliever; doubter, skeptic, secularist, empiricist; heathen, heretic, infidel, pagan.

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

a person who holds neither of two opposing positions on a topic: Socrates was an agnostic on the subject of immortality.

of or relating to agnostics or their doctrines, attitudes, or beliefs.

asserting the uncertainty of all claims to knowledge.