Definition of "unbelief"

And he coulde there ſhewe no myracles butt leyd his hondꝭ apon a feawe ſicke foolke ãd healed thẽ. And he merveyled at their vnbelefe.

1526, [William Tyndale, transl.], The Newe Testamẽt […] (Tyndale Bible), [Worms, Germany: Peter Schöffer], Mark vj:[5–6], folio lj, recto

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

1931, William Faulkner, Sanctuary, Vintage, published 1993, page 35

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.

2009, Diarmaid MacCulloch, A History of Christianity, Penguin, published 2010, page 781