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]