The Collaborative International Dictionary of English v.0.48:

Dialogue \Di"a*logue\ (?; 115), n. [OE. dialogue, L. dialogus,
   fr. Gr. ?, fr. ? to converse, dia` through + ? to speak: cf.
   F. dialogue. See Legend.]
   1. A conversation between two or more persons; particularly,
      a formal conservation in theatrical performances or in
      scholastic exercises.
      [1913 Webster]

   2. A written composition in which two or more persons are
      represented as conversing or reasoning on some topic; as,
      the Dialogues of Plato.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dialogue \Di"a*logue\, v. i. [Cf. F. dialoguer.]
   To take part in a dialogue; to dialogize. [R.] --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dialogue \Di"a*logue\, v. t.
   To express as in dialogue. [R.]
   [1913 Webster]

         And dialogued for him what he would say. --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dialogue
    n 1: a conversation between two persons [syn: dialogue,
         dialog, duologue]
    2: the lines spoken by characters in drama or fiction [syn:
       dialogue, dialog]
    3: a literary composition in the form of a conversation between
       two people; "he has read Plato's Dialogues in the original
       Greek" [syn: dialogue, dialog]
    4: a discussion intended to produce an agreement; "the buyout
       negotiation lasted several days"; "they disagreed but kept an
       open dialogue"; "talks between Israelis and Palestinians"
       [syn: negotiation, dialogue, talks]

Moby Thesaurus II by Grady Ward, 1.0:

142 Moby Thesaurus words for "dialogue":
   Grand Guignol, Passion play, Tom show, airing, analysis,
   antimasque, audience success, ballet, bomb, broadcast drama,
   bull session, burlesque show, buzz session, canvassing, charade,
   chat, chinfest, cliff hanger, closet drama, colloquium, colloquy,
   comedy drama, communication, confab, confabulation, conference,
   consideration, conversation, converse, critical success,
   daytime serial, debate, debating, deliberation, dialectic,
   discussion, documentary drama, drama, dramalogue, dramatic play,
   dramatic series, duodrama, duologue, epic theater, examination,
   exchange of views, experimental theater, extravaganza, failure,
   flop, forum, gasser, giveaway, happening, hit, hit show, huddle,
   improvisational drama, investigation, joint discussion,
   legitimate drama, logical analysis, logical discussion, masque,
   meeting, melodrama, minstrel show, miracle, miracle play,
   monodrama, monologue, morality, morality play, music drama,
   musical revue, mystery, mystery play, open discussion, open forum,
   opera, pageant, palaver, panel discussion, panel show, pantomime,
   parley, pastoral, pastoral drama, piece, play, playlet,
   problem play, psychodrama, question-and-answer session, quiz show,
   radio drama, rap, rap session, review, revue, seminar,
   sensational play, serial, show, sitcom, situation comedy, sketch,
   skit, soap, soap opera, sociodrama, spectacle, speech, stage play,
   stage show, straight drama, study, success, suspense drama,
   symposium, tableau, tableau vivant, talk, talk show, talkfest,
   teleplay, television drama, television play, tete-a-tete,
   theater of cruelty, total theater, town meeting, treatment,
   trialogue, variety show, vaudeville, vaudeville show, vehicle,
   ventilation, word-of-mouth success, words, work