(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.

plural of Old Believer

(rare) Someone who hides their belief.

plural of make believe

plural of crypto-believer

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.

present participle of make believe

A phenomenon in which witnesses to a staged event continue to believe in its authenticity even after it has been debunked.

(idiomatic) An emphatic form of believe me: you (the subject) had better believe me (the speaker).

(idiomatic, chiefly in the negative) To believe that something which one directly sees is truly the case.