The Collaborative International Dictionary of English v.0.48:

garishness \gar"ish*ness\ n.
   1. tasteless showiness.

   Syn: flashiness, gaudiness, loudness, meretriciousness,
        tawdriness, glitz.
        [WordNet 1.5]

   2. strident color or excessive ornamentation.

   Syn: gaudiness.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Garish \Gar"ish\ (g[^a]r"[i^]sh), a. [Cf. OE. gauren to stare;
   of uncertain origin. Cf. gairish.]
   1. Showy; dazzling; ostentatious; attracting or exciting
      attention. "The garish sun." "A garish flag." --Shak. "In
      . . . garish colors." --Asham. "The garish day." --J. H.
      Newman.
      [1913 Webster]

            Garish like the laughters of drunkenness. --Jer.
                                                  Taylor.
      [1913 Webster]

   2. Gay to extravagance; flighty.
      [1913 Webster]

            It makes the mind loose and garish.   --South.
      -- Gar"ish*ly, adv. -- Gar"ish*ness, n. --Jer. Taylor.
      [1913 Webster]

WordNet (r) 3.0 (2006):

garishness
    n 1: tasteless showiness [syn: flashiness, garishness,
         gaudiness, loudness, brashness, meretriciousness,
         tawdriness, glitz]
    2: strident color or excessive ornamentation [syn: garishness,
       gaudiness]