The Collaborative International Dictionary of English v.0.48:

Denounce \De*nounce"\, v. t. [imp. & p. p. Denounced; p. pr. &
   vb. n. Denouncing.] [F. d['e]noncer, OF. denoncier, fr. L.
   denuntiare, denunciare; de- + nunciare, nuntiare, to
   announce, report, nuntius a messenger, message. See Nuncio,
   and cf. Denunciate.]
   1. To make known in a solemn or official manner; to declare;
      to proclaim (especially an evil). [Obs.]
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            Denouncing wrath to come.             --Milton.
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            I denounce unto you this day, that ye shall surely
            perish.                               --Deut. xxx.
                                                  18.
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   2. To proclaim in a threatening manner; to threaten by some
      outward sign or expression.
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            His look denounced desperate.         --Milton.
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   3. To point out as deserving of reprehension or punishment,
      etc.; to accuse in a threatening manner; to invoke censure
      upon; to stigmatize.
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            Denounced for a heretic.              --Sir T. More.
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            To denounce the immoralities of Julius C[ae]sar.
                                                  --Brougham.
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WordNet (r) 3.0 (2006):

denounce
    v 1: speak out against; "He denounced the Nazis"
    2: to accuse or condemn or openly or formally or brand as
       disgraceful; "He denounced the government action"; "She was
       stigmatized by society because she had a child out of
       wedlock" [syn: stigmatize, stigmatise, brand,
       denounce, mark]
    3: announce the termination of, as of treaties
    4: give away information about somebody; "He told on his
       classmate who had cheated on the exam" [syn: denounce,
       tell on, betray, give away, rat, grass, shit,
       shop, snitch, stag]

Moby Thesaurus II by Grady Ward, 1.0:

103 Moby Thesaurus words for "denounce":
   accuse, allege, anathematize, anathemize, animadvert on, arraign,
   article, assail, attack, attaint, be imminent, betray, blacklist,
   blame, bludgeon, book, brand, bring accusation, bring charges,
   bring home to, bring to book, bulldoze, call to account,
   cast blame upon, cast reflection upon, censure, charge, cite,
   comminate, complain, complain against, condemn, convict, criticize,
   cry down, cry out against, cry out on, cry shame upon, damn, decry,
   denunciate, doom, excommunicate, fasten on, fasten upon,
   find guilty, finger, forebode, fulminate against,
   hang something on, impeach, implicate, imply, impugn, impute,
   incriminate, indict, inform, inform against, inform on, insinuate,
   intimidate, inveigh against, knock, lay charges, lodge a complaint,
   lodge a plaint, look threatening, lower, menace, pass sentence on,
   penalize, pillory, pin on, prefer charges, press charges,
   pronounce judgment, pronounce sentence, proscribe, put on report,
   rap, reflect upon, report, reprehend, reproach, reprobate, reveal,
   revile, ridicule, sentence, shake up, skin, stigmatize,
   take to task, task, taunt with, tax, threaten, twit,
   utter threats against, vilify, vituperate, warn