The Collaborative International Dictionary of English v.0.48:

Grandiose \Gran"di*ose"\, a. [F. grandiose, It. grandioso. See
   Grand.]
   1. Impressive or elevating in effect; imposing; splendid;
      striking; -- in a good sense.
      [1913 Webster]

            The tone of the parts was to be perpetually kept
            down in order not to impair the grandiose effect of
            the whole.                            --M. Arnold.
      [1913 Webster]

            The grandiose red tulips which grow wild. --C.
                                                  Kingsley.
      [1913 Webster]

   2. Characterized by affectation of grandeur or splendor;
      flaunting; turgid; bombastic; -- in a bad sense; as, a
      grandiose style.
      [1913 Webster]

WordNet (r) 3.0 (2006):

grandiose
    adj 1: impressive because of unnecessary largeness or grandeur;
           used to show disapproval
    2: affectedly genteel [syn: grandiose, hifalutin,
       highfalutin, highfaluting, hoity-toity, la-di-da]