unbeliever

n. one who does not believe, one who has no faith, skeptic

An infidel (literally "one without faith") is an English word meaning "one who doubts or rejects central tenets of a religion or has no religious beliefs", especially in reference to Christianity or Islam. When used in an Islamic sense it serves as a translation of the Arabic word kafir (literally "one who denies the blessings of God") referring to those who deny the existence of God, worship more than one god, or worship something else other than God. "Infidel" and "kafir" are often regarded as offensive.
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Noun
1. someone who refuses to believe (as in a divinity)
(synonym) disbeliever, nonbeliever
(hypernym) nonreligious person
(hyponym) atheist

(n.)
One who does not believe; an incredulous person; a doubter; a skeptic.
  

(n.)
A disbeliever; especially, one who does not believe that the Bible is a divine revelation, and holds that Christ was neither a divine nor a supernatural person; an infidel; a freethinker.
  

n.
غير متيقن, غير معتقد, بے دين, کافر