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):

garishly
    adv 1: in a tastelessly garish manner; "the temple was garishly
           decorated with bright plastic flowers" [syn: garishly,
           tawdrily, gaudily]