A strict follower of a doctrine. / One who believes dogmatically in something regardless of evidence or even conclusive proof that the thing is false or was staged; one who has true-believer syndrome.

alternative spelling of nonbeliever

plural of true believer

plural of non-believer

plural of Old Believer

(religion) Any of those who separated from the official Russian Orthodox Church after 1666 as a protest against church reforms introduced by Patriarch Nikon between 1652 and 1666. They continue liturgical practices which predate the reforms.

(rare) Someone who hides their belief.

plural of crypto-believer

someone who shares one's faith; a brother in faith

Alternative spelling of true-believer syndrome