Agnostic

adj. atheistic

n. one who is unsure whether or not God exists; person who refuses to declare belief in the existence or nonexistence of God; skeptic, person who is doubting or suspicious about something

Agnosticism (from the Greek a, meaning "without", and gnosticism or gnosis, meaning "knowledge") is the philosophical view that the truth value of certain claims—particularly metaphysical claims regarding theology, afterlife or the existence of God, gods, deities, or even ultimate reality—is unknown or, depending on the form of agnosticism, inherently unknowable due to the nature of subjective experience. In western laypersons terms, an Agnostic is one who doesn't believe you can prove there's a God, but doesn't deny it's possible a God may exist.
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Noun
1. a person who doubts truth of religion
(synonym) doubter
(hypernym) nonreligious person
Adjective
1. uncertain of all claims to knowledge
(synonym) agnostical
(antonym) gnostic
(similar) nescient, unbelieving

(n.)
One who professes ignorance, or denies that we have any knowledge, save of phenomena; one who supports agnosticism, neither affirming nor denying the existence of a personal Deity, a future life, etc.
  

(a.)
Professing ignorance; involving no dogmatic; pertaining to or involving agnosticism.
  

filoz. agnostic