Source : Webster's Revised Unabridged Dictionary (1913)

Defamatory \De*fam"a*to*ry\, a.
   Containing defamation; injurious to reputation; calumnious;
   slanderous; as, defamatory words; defamatory writings.

Source : WordNet®

defamatory
     adj : (used of statements) harmful and often untrue; tending to
           discredit or malign [syn: {calumniatory}, {calumnious},
            {denigrative}, {denigrating}, {denigratory}, {libellous},
            {libelous}, {slanderous}]