1. The withholding of belief; doubt; incredulity; skepticism.
2. Disbelief; especially, disbelief of divine revelation, or in a divine providence or scheme of redemption. Blind unbelief is sure to err, And scan his work in vain. Cowper.
-- See Disbelief.
ETYMOLOGY = Pref. un- not + belief: compare with (Anglo-Saxon) ungeleáfa.