Source : Webster's Revised Unabridged Dictionary (1913)

Nullify \Nul"li*fy\, v. t. [imp. & p. p. {Nullified}; p. pr. &
   vb. n. {Nullifying}.] [L. nullificare; nullus none + -ficare
   (in comp.) to make. See {Null}, a., and {-fy}.]
   To make void; to render invalid; to deprive of legal force or
   efficacy.

         Such correspondence would at once nullify the
         conditions of the probationary system.   --I. Taylor.

   Syn: To abrogate; revoke; annul; repeal; invalidate; cancel.
        See {Abolish}.