Noun

(en-noun)

An absence (or rejection) of belief, especially religious belief

* 1526 , (William Tyndale), trans. Bible , Mark VI:

And he coulde there shewe no myracles butt leyd his hondes apon a feawe sicke foolke and healed them. And he merveyled at their unbelefe .

* 1931 , (William Faulkner), Sanctuary , Vintage 1993, p. 35:

On hands and knees he looked at the empty siding and up at the sunfilled sky with unbelief and despair.

* 2009 , (Diarmaid MacCulloch), A History of Christianity , Penguin 2010, p. 781:

Soon Spinoza was regarded as the standard-bearer for unbelief , even though pervading his carefully-worded writings there is a clear notion of a divine spirit inhabiting the world, and a profound sense of wonder and reverence for mystery.

Noun

(-)

Unwillingness or inability to believe; doubt about the truth or verisimilitude of something; disbelief.

* 1916 , Edgar Rice Burroughs, Tarzan and the Jewels of Opar , ch. 24:

Wide went her eyes in wonder and incredulity , as she beheld this seeming apparition risen from the dead.

* {{quote-book, year=1963, author=(Margery Allingham), title=(The China Governess)

, chapter=8 citation , passage=It was a casual sneer, obviously one of a long line. There was hatred behind it, but of a quiet, chronic type, nothing new or unduly virulent, and he was taken aback by the flicker of amazed incredulity that passed over the younger man's ravaged face.}}

(rare) Religious disbelief, lack of faith.