Source : Webster's Revised Unabridged Dictionary (1913)

Disavow \Dis`a*vow"\, v. t. [imp. & p. p. {Disavowed}; p. pr. &
   vb. n. {Disavowing}.] [F. d['e]savouer; pref. d['e]s- (L.
   dis-) + avouer to avow. See {Avow}, and cf. {Disavouch}.]
   1. To refuse strongly and solemnly to own or acknowledge; to
      deny responsibility for, approbation of, and the like; to
      disclaim; to disown; as, he was charged with embezzlement,
      but he disavows the crime.

            A solemn promise made and disavowed.  --Dryden.

   2. To deny; to show the contrary of; to disprove.

            Yet can they never Toss into air the freedom of my
            birth, Or disavow my blood Plantagenet's. --Ford.

Source : WordNet®

disavow
     v : refuse to acknowledge; disclaim knowledge of; responsibility
         for, or association with; "Her husband disavowed her
         after 30 years of marriage and six children" [ant: {avow}]