Source : Webster's Revised Unabridged Dictionary (1913)

Calumniatory \Ca*lum"ni*a*to*ry\, a.
   Containing calumny; slanderous. --Montagu.

Source : WordNet®

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