[UN-2 4.] trans. To give up belief in; to discard or abandon (belief).
1605. Daniel, Queens Arcadia, V. iv. (1606), Kiij. How were I cleerd of griefe, Had I the power to vnbeleeue beliefe.
1795. Paine, Age of Reason, II. 8. To believe therefore the Bible to be true, we must unbelieve all our belief in the moral justice of God.
1837. Ht. Martineau, Soc. Amer., II. 38, note. You know nothing of those people. They will believe everything, and unbelieve nothing.