Unwillingness or inability to believe; doubt about the truth or verisimilitude of something; disbelief. / (rare) Religious disbelief, lack of faith.

Skeptical, disbelieving, or unable to believe. / Expressing or indicative of incredulity. / (largely obsolete, now only nonstandard) Difficult to believe; incredible.

(rare) Incredulity; the state of being skeptical or in disbelief.

In an incredulous manner; tending to disbelieve; skeptically.

plural of incredulity