The Collaborative International Dictionary of English v.0.48:

Conventionalism \Con*ven"tion*al*ism\, n.
   1. That which is received or established by convention or
      arbitrary agreement; that which is in accordance with the
      fashion, tradition, or usage.
      [1913 Webster]

            All the artifice and conventionalism of life.
                                                  --Hawthorne.
      [1913 Webster]

            They gaze on all with dead, dim eyes, -- wrapped in
            conventionalisms, . . . simulating feelings
            according to a received standard.     --F. W.
                                                  Robertson.
      [1913 Webster]

   2. (Fine Arts) The principles or practice of
      conventionalizing. See Conventionalize, v. t.
      [1913 Webster]

WordNet (r) 3.0 (2006):

conventionalism
    n 1: orthodoxy as a consequence of being conventional [syn:
         conventionality, convention, conventionalism] [ant:
         unconventionality]