KJV Dictionary Definition: unbelief
1. Incredulity; the withholding of belief; as, unbelief is blind.
2. Infidelity; disbelief of divine revelation.
3. In the New Testament, disbelief of the truth of the gospel, rejection of Christ as the Savior of men, and of the doctrines he taught; distrust of God's promises and faithfulness, &c. Matt. 13. Mark 16. Heb. 3. Rom. 4.
4. Weak faith. Mark 9.