The Collaborative International Dictionary of English v.0.48:

Manifesto \Man`i*fes"to\, n.; pl. Manifestoes. [It. manifesto.
   See Manifest, n. & a.]
   A public declaration, usually of a prince, sovereign, or
   other person claiming large powers, showing his intentions,
   or proclaiming his opinions and motives in reference to some
   act done or contemplated by him; as, a manifesto declaring
   the purpose of a prince to begin war, and explaining his
   motives. --Bouvier.
   [1913 Webster]

         it was proposed to draw up a manifesto, setting forth
         the grounds and motives of our taking arms. --Addison.
   [1913 Webster]

         Frederick, in a public manifesto, appealed to the
         Empire against the insolent pretensions of the pope.
                                                  --Milman.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

53 Moby Thesaurus words for "manifesto":
   affidavit, affirmance, affirmation, allegation, announcement,
   annunciation, assertion, asseveration, averment, avouchment,
   avowal, bulletin board, circular, communique, conclusion, creed,
   declaration, deposition, dictum, edict, encyclical, enunciation,
   ipse dixit, notice, notification, position, position paper,
   positive declaration, predicate, predication, proclamation,
   profession, program, programma, pronouncement, pronunciamento,
   proposition, protest, report, say, say-so, saying,
   solemn declaration, stance, stand, statement, statement of belief,
   ukase, utterance, vouch, white book, white paper, word