Source : Webster's Revised Unabridged Dictionary (1913)

Conventional \Con*ven"tion*al\, a. [L. conventionalis: cf. F.
   conventionnel.]
   1. Formed by agreement or compact; stipulated.

            Conventional services reserved by tenures upon
            grants, made out of the crown or knights' service.
                                                  --Sir M. Hale.

   2. Growing out of, or depending on, custom or tacit
      agreement; sanctioned by general concurrence or usage;
      formal. ``Conventional decorum.'' --Whewell.

            The conventional language appropriated to monarchs.
                                                  --Motley.

            The ordinary salutations, and other points of social
            behavior, are conventional.           --Latham.

   3. (Fine Arts)
      (a) Based upon tradition, whether religious and historical
          or of artistic rules.
      (b) Abstracted; removed from close representation of
          nature by the deliberate selection of what is to be
          represented and what is to be rejected; as, a
          conventional flower; a conventional shell. Cf.
          {Conventionalize}, v. t.

Source : WordNet®

conventional
     adj 1: following accepted customs and proprieties; "conventional
            wisdom"; "she had strayed from the path of
            conventional behavior"; "conventional forms of
            address" [ant: {unconventional}, {unconventional}]
     2: conforming with accepted standards; "a conventional view of
        the world" [syn: {established}]
     3: (weapons) using non-nuclear energy for propulsion or
        destruction; "conventional warfare"; "conventional
        weapons" [ant: {nuclear}]
     4: unimaginative and conformist; "conventional bourgeois
        lives"; "conventional attitudes" [ant: {unconventional}]
     5: represented in simplified or symbolic form [syn: {formal}, {schematic}]
     6: in accord with or being a tradition or practice accepted
        from the past; "a conventional church wedding with the
        bride in traditional white"; "the conventional handshake"
     7: rigidly formal or bound by convention; "their ceremonious
        greetings did not seem heartfelt" [syn: {ceremonious}]