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.

(archaic) second-person singular simple present form of believe

(archaic) third-person singular simple present indicative form of belie

(archaic) second-person singular simple present form of belie

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

(intransitive, chiefly UK) To appear implausible or unbelievable.

Alternative spelling of true-believer syndrome

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

(transitive) To ascribe existence to. / (transitive) To believe that (something) is right or desirable. / (transitive) To have confidence in the ability or power of.

simple past tense and past participle of believe in