What is Annul?

Legal Definition
To cancel; make void; destroy. To annul a judgment or judicial proceeding is to deprive it of all force and operation, either ab initio or prospectively as to future transactions. Wait v. Wait, 4 Barb. (N. Y.) 205; Woodson v. Skinner, 22 Mo. 24; In re Morrow's Estate, 204 Pa. 484, 54 Atl. 342.
-- Black's Law Dictionary
Legal Definition
To nullify; to set at naught; to make void. See 22 Mo. 24.
-- Ballentine's Law Dictionary