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]

Moby Thesaurus II by Grady Ward, 1.0:

103 Moby Thesaurus words for "grandiose":
   Babylonian, Corinthian, Gongoresque, Johnsonian, affected,
   ambitious, august, awe-inspiring, awful, barbaric, bedizened,
   big-sounding, bombastic, convoluted, cosmic, declamatory, deluxe,
   elaborate, elegant, elevated, euphuistic, extravagant, fancy, fine,
   flamboyant, flaming, flash, flashy, flaunting, florid, fulsome,
   fustian, garish, gaudy, glorious, grand, grandiloquent,
   grandisonant, high-flowing, high-flown, high-flying, high-sounding,
   highfalutin, histrionic, imposing, impressive, inflated, inkhorn,
   labyrinthine, lexiphanic, lofty, lordly, lurid, luxurious,
   magnificent, magniloquent, majestic, melodramatic, meretricious,
   monumental, noble, orotund, ostentatious, overambitious, overdone,
   overelaborate, overinvolved, overwhelming, overwrought, palatial,
   pedantic, plush, pompous, posh, pretentious, princely, proud,
   rhetorical, ritzy, royal, sensational, sensationalistic,
   sententious, showy, sonorous, splendacious, splendid,
   splendiferous, stately, stilted, sumptuous, superb, superfancy,
   superfine, swank, swanky, swell, tall, tortuous, unfathomable,
   utopian, vast, visionary