The Collaborative International Dictionary of English v.0.48:

Luxuriant \Lux*u"ri*ant\, a. [L. luxurians, p. pr. of luxuriare:
   cf. F. luxuriant. See Luxuriate.]
   1. Exuberant in growth; rank; excessive; profuse; very
      abundant; as, a luxuriant growth of grass; luxuriant
      foliage.
      [1913 Webster]

            Prune the luxuriant, the uncouth refine. --Pope.
      [1913 Webster]

   2. Producing luxuriant growth; very fertile; -- of soil.
      [PJC]

   3. Having or producing an abundance of elaborate details;
      unrestrained; -- of imagery or ornamentation.
      [PJC]

   Luxuriant flower (Bot.), one in which the floral envelopes
      are overdeveloped at the expense of the essential organs.
      [1913 Webster]

WordNet (r) 3.0 (2006):

luxuriant
    adj 1: marked by complexity and richness of detail; "an
           elaborate lace pattern" [syn: elaborate, luxuriant]
    2: displaying luxury and furnishing gratification to the senses;
       "an epicurean banquet"; "enjoyed a luxurious suite with a
       crystal chandelier and thick oriental rugs"; "Lucullus spent
       the remainder of his days in voluptuous magnificence"; "a
       chinchilla robe of sybaritic lavishness" [syn: epicurean,
       luxurious, luxuriant, sybaritic, voluptuary,
       voluptuous]
    3: produced or growing in extreme abundance; "their riotous
       blooming" [syn: exuberant, lush, luxuriant, profuse,
       riotous]

Moby Thesaurus II by Grady Ward, 1.0:

136 Moby Thesaurus words for "luxuriant":
   abounding, abundant, adorned, affluent, all-sufficing, ample,
   aplenty, arabesque, baroque, befrilled, blooming, bottomless,
   bounteous, bountiful, bursting, bursting out, busy, chichi,
   colored, copious, creative, decorated, deluxe, dense, diffuse,
   effuse, elaborate, elegant, embellished, embroidered, epidemic,
   exhaustless, extravagant, exuberant, fancy, fat, fecund, fertile,
   festooned, figurative, figured, fine, flamboyant, flashy, florid,
   flourishing, flowery, flush, frilly, fructiferous, fruitful, full,
   fussy, galore, garish, gaudy, generous, gross, heavy, high-wrought,
   impenetrable, in plenty, in quantity, inexhaustible, jungled,
   jungly, labored, lavish, liberal, luscious, lush, luxurious, many,
   maximal, moresque, much, numerous, opulent, ornate, ostentatious,
   overcharged, overdone, overelaborate, overelegant, overflowing,
   overgrown, overlabored, overloaded, overrun, overworked,
   overwrought, palatial, picturesque, plenitudinous, plenteous,
   plentiful, plenty, plush, pregnant, pretty-pretty, prevailing,
   prevalent, prodigal, productive, profuse, profusive, proliferous,
   prolific, purple, rampant, rank, replete, rich, rife, riotous,
   rococo, running over, seminal, showy, sumptuous, superabundant,
   swarming, teeming, thick, thriving, uberous, unweeded, wealthy,
   weed-choked, weed-ridden, weedy, well-found, well-furnished,
   well-provided, well-stocked, wholesale