The Collaborative International Dictionary of English v.0.48:

Luxury \Lux"u*ry\, n.; pl. Luxuries. [L. luxuria, fr. luxus:
   cf. F. luxure.]
   1. A free indulgence in costly food, dress, furniture, or
      anything expensive which gratifies the appetites or
      tastes.
      [1913 Webster]

            Riches expose a man to pride and luxury.
                                                  --Spectator.
      [1913 Webster]

   2. Anything which pleases the senses, is not necessary for
      life, and is also costly, or difficult to obtain; an
      expensive rarity; as, silks, jewels, and rare fruits are
      luxuries; in some countries ice is a great luxury.
      Contrasted to necessity.
      [1913 Webster]

            He cut the side of a rock for a garden, and, by
            laying on it earth, furnished out a kind of luxury
            for a hermit.                         --Addison.
      [1913 Webster]

   3. Lechery; lust. [Obs.] --Shak.
      [1913 Webster]

            Luxury is in wine and drunkenness.    --Chaucer.
      [1913 Webster]

   4. Luxuriance; exuberance. [Obs.] --Bacon.

   Syn: Voluptuousness; epicurism; effeminacy; sensuality;
        lasciviousness; dainty; delicacy; gratification.
        [1913 Webster]

WordNet (r) 3.0 (2006):

luxury
    n 1: something that is an indulgence rather than a necessity
    2: the quality possessed by something that is excessively
       expensive [syn: lavishness, luxury, sumptuosity,
       sumptuousness]
    3: wealth as evidenced by sumptuous living [syn: luxury,
       luxuriousness, opulence, sumptuousness]

Moby Thesaurus II by Grady Ward, 1.0:

171 Moby Thesaurus words for "luxury":
   Babylonian splendor, Cyrenaic hedonism, Cyrenaicism, Easy Street,
   affluence, amenity, amusement, animal pleasure, appeal,
   appealingness, appetite, appetitiveness, attractiveness,
   bed of roses, bedizenment, bewitchment, bodily pleasure,
   brilliance, captivation, carnal delight, charm, clover, comfort,
   confidence, content, contentment, coziness, creature comforts,
   dainty, delicacy, delight, delightfulness, duplication,
   duplication of effort, ease, easy circumstances, elaborateness,
   elegance, embellishment, enchantment, endpleasure, enjoyment,
   enravishment, entertainment, entrancement, epicureanism, epicurism,
   ethical hedonism, euphoria, expendable, expletive, exquisiteness,
   extra, extravagance, fascination, fat, featherbedding, felicity,
   filling, fleshpots, forepleasure, frill, frills, frippery,
   fruition, fun, gingerbread, glamour, glory, gorgeousness, grace,
   gracious life, gracious living, grandeur, grandiosity, grandness,
   gratification, great satisfaction, gusto, happiness,
   hearty enjoyment, hedonic calculus, hedonics, hedonism,
   imposingness, impressiveness, indulgence, intellectual pleasure,
   invitingness, joie de vivre, keen pleasure, kicks, lap of luxury,
   lavishness, life of ease, loaves and fishes, loveliness,
   luxuriousness, magnificence, majesty, needlessness, nobility,
   opulence, ornamentation, overadornment, overlap, padding,
   payroll padding, physical pleasure, pleasure, pleasure principle,
   pleasure-seeking, pleonasm, plushness, poshness, prolixity,
   prosperity, prosperousness, proudness, psychological hedonism,
   quiet pleasure, redundance, redundancy, relish, resplendence,
   richness, ritziness, satisfaction, security, self-gratification,
   self-indulgence, sensual pleasure, sensualism, sensuality,
   sensualness, sensuous pleasure, sensuousness, sexual pleasure,
   splendidness, splendiferousness, splendor, state, stateliness,
   success, sumptuousness, superfluity, superfluousness,
   sweetness of life, sybaritism, tantalizingness, tautology,
   temptingness, the affluent life, the good life, thriving condition,
   titillation, treat, unchastity, unnecessariness, upward mobility,
   velvet, verbosity, voluptuousness, weal, wealth, welfare,
   well-being, winningness, winsomeness, witchery, zest