The Collaborative International Dictionary of English v.0.48:

Announce \An*nounce"\, v. t. [imp. & p. p. Announced; p. pr. &
   vb. n. Announcing.] [OF. anoncier, F. annoncer, fr. L.
   annuntiare; ad + nuntiare to report, relate, nuntius
   messenger, bearer of news. See Nuncio, and cf.
   Annunciate.]
   [1913 Webster]
   1. To give public notice, or first notice of; to make known;
      to publish; to proclaim.
      [1913 Webster]

            Her [Q. Elizabeth's] arrival was announced through
            the country by a peal of cannon from the ramparts.
                                                  --Gilpin.
      [1913 Webster]

   2. To pronounce; to declare by judicial sentence.
      [1913 Webster]

            Publish laws, announce
            Or life or death.                     --Prior.
      [1913 Webster]

   Syn: To proclaim; publish; make known; herald; declare;
        promulgate.

   Usage: To Publish, Announce, Proclaim, Promulgate. We
          publish what we give openly to the world, either by
          oral communication or by means of the press; as, to
          publish abroad the faults of our neighbors. We
          announce what we declare by anticipation, or make
          known for the first time; as, to announce the speedy
          publication of a book; to announce the approach or
          arrival of a distinguished personage. We proclaim
          anything to which we give the widest publicity; as, to
          proclaim the news of victory. We promulgate when
          we proclaim more widely what has before been known by
          some; as, to promulgate the gospel.
          [1913 Webster]

WordNet (r) 3.0 (2006):

announce
    v 1: make known; make an announcement; "She denoted her feelings
         clearly" [syn: announce, denote]
    2: announce publicly or officially; "The President declared war"
       [syn: announce, declare]
    3: give the names of; "He announced the winners of the spelling
       bee"
    4: foreshadow or presage [syn: announce, annunciate,
       harbinger, foretell, herald]

Moby Thesaurus II by Grady Ward, 1.0:

112 Moby Thesaurus words for "announce":
   advertise, affirm, allege, annunciate, antecede, antedate,
   anticipate, argue, assert, assever, asseverate, attest, augur,
   aver, avouch, avow, be before, be early, bespeak, betoken, blazon,
   break the news, bring word, broadcast, bruit about, circulate,
   come before, communicate, confirm, contend, declare,
   declare roundly, disclose, divulge, enunciate, express, forebode,
   forecast, forerun, foreshow, foretell, give a report, give notice,
   give tidings of, harbinger, have, herald, hint at, hold, impart,
   inform, insist, intimate, issue a manifesto, issue a statement,
   lay down, maintain, make a statement, make an announcement,
   make known, make public, manifesto, notify, portend, preannounce,
   precede, precurse, predate, predicate, predict, preexist,
   preindicate, presage, present, proclaim, profess, promulgate,
   pronounce, propound, protest, publicize, publish,
   publish a manifesto, put, put forth, put it, put out, rehearse,
   relate, report, reveal, rumor, run before, say, set down,
   set forth, show forth, signal, sound, speak, speak out, speak up,
   stand for, stand on, state, submit, suggest, tell, testify,
   usher in, witness, write up