Source : Webster's Revised Unabridged Dictionary (1913)

Imprecation \Im`pre*ca"tion\, n. [L. imprecatio: cf. F.
   impr['e]cation.]
   The act of imprecating, or invoking evil upon any one; a
   prayer that a curse or calamity may fall on any one; a curse.

         Men cowered like slaves before such horrid
         imprecations.                            --Motley.

   Syn: Malediction; curse; execration; anathema. See
        {Malediction}.

Source : WordNet®

imprecation
     n 1: the act of calling down a curse that invokes evil (and
          usually serves as an insult); "he suffered the
          imprecations of the mob" [syn: {malediction}]
     2: a slanderous accusation