Source : Webster's Revised Unabridged Dictionary (1913)

Annul \An*nul"\, v. t. [imp. & p. p. {Annulled}; p. pr. & vb. n.
   {Annulling}.] [F. annuler, LL. annullare, annulare, fr. L. ad
   to + nullus none, nullum, neut., nothing. See {Null}, a.]
   1. To reduce to nothing; to obliterate.

            Light, the prime work of God, to me's extinct. And
            all her various objects of delight Annulled.
                                                  --Milton.

   2. To make void or of no effect; to nullify; to abolish; to
      do away with; -- used appropriately of laws, decrees,
      edicts, decisions of courts, or other established rules,
      permanent usages, and the like, which are made void by
      component authority.

            Do they mean to annul laws of inestimable value to
            our liberties?                        --Burke.

   Syn: To abolish; abrogate; repeal; cancel; reverse; rescind;
        revoke; nullify; destroy. See {Abolish}.

Source : WordNet®

annul
     v 1: declare invalid; "The contract was annulled"; "void a plea"
          [syn: {invalidate}, {quash}, {void}, {avoid}, {nullify}]
          [ant: {validate}]
     2: annul by recalling or rescinding; "He revoked the ban on
        smoking"; "lift an embargo"; "vacate a death sentence"
        [syn: {revoke}, {lift}, {countermand}, {reverse}, {repeal},
         {overturn}, {rescind}, {vacate}]
     [also: {annulling}, {annulled}]

annulling
     See {annul}