The Collaborative International Dictionary of English v.0.48:

Imprecate \Im"pre*cate\, v. t. [imp. & p. p. Imprecated; p.
   pr. & vb. n. Imprecating.] [L. imprecatus, p. p. of
   imprecari to imprecate; pref. im- in, on + precari to pray.
   See Pray.]
   1. To call down by prayer, as something hurtful or
      calamitous.
      [1913 Webster]

            Imprecate the vengeance of Heaven on the guilty
            empire.                               --Mickle.
      [1913 Webster]

   2. To invoke evil upon; to curse; to swear at.
      [1913 Webster]

            In vain we blast the ministers of Fate,
            And the forlorn physicians imprecate. --Rochester.
      [1913 Webster]

WordNet (r) 3.0 (2006):

imprecate
    v 1: wish harm upon; invoke evil upon; "The bad witch cursed the
         child" [syn: curse, beshrew, damn, bedamn,
         anathemize, anathemise, imprecate, maledict] [ant:
         bless]
    2: utter obscenities or profanities; "The drunken men were
       cursing loudly in the street" [syn: curse, cuss,
       blaspheme, swear, imprecate]