The Collaborative International Dictionary of English v.0.48:

Oration \O*ra"tion\, v. i.
   To deliver an oration. --Donne.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Oration \O*ra"tion\, n.[L. oratio, fr. orare to speak, utter,
   pray. See Oral, Orison.]
   An elaborate discourse, delivered in public, treating an
   important subject in a formal and dignified manner;
   especially, a discourse having reference to some special
   occasion, as a funeral, an anniversary, a celebration, or the
   like; -- distinguished from an argument in court, a popular
   harangue, a sermon, a lecture, etc.; as, Webster's oration at
   Bunker Hill.
   [1913 Webster]

         The lord archbishop . . . made a long oration. --Bacon.
   [1913 Webster]

   Syn: Address; speech. See Harangue.
        [1913 Webster]

WordNet (r) 3.0 (2006):

oration
    n 1: an instance of oratory; "he delivered an oration on the
         decline of family values"

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "oration":
   address, after-dinner speech, allocution, chalk talk, debate,
   declamation, declaration, diatribe, discourse, eulogy, exhortation,
   filibuster, forensic, forensic address, formal speech,
   funeral oration, harangue, homily, hortatory address, inaugural,
   inaugural address, invective, jeremiad, lecture, monologue,
   panegyric, pep talk, peroration, philippic, pitch, prepared speech,
   prepared text, public speech, reading, recital, recitation,
   sales talk, salutatory, salutatory address, say, screed,
   set speech, speech, speechification, speeching, spiel, talk,
   talkathon, tirade, valediction, valedictory, valedictory address