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]

WordNet (r) 3.0 (2006):

manifesto
    n 1: a public declaration of intentions (as issued by a
         political party or government) [syn: manifesto,
         pronunciamento]

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



Bouvier's Law Dictionary, Revised 6th Ed (1856):

MANIFESTO. A solemn declaration, by the constituted authorities of a nation,
which contains the reasons for its public acts towards another.
     2. On the declaration of war, a manifesto is usually issued in which
the nation declaring the war, states the reasons for so doing. Vattel, liv.
3, c. 4, Sec. 64; Wolff, Sec. 1187. See Anti-Manifesto.