The Collaborative International Dictionary of English v.0.48:

Dilettante \Dil`et*tan"te\, n.; pl. Dilettanti. [It., prop. p.
   pr. of dillettare to take delight in, fr. L. delectare to
   delight. See Delight, v. t.]
   An admirer or lover of the fine arts; popularly, an amateur;
   especially, one who follows an art or a branch of knowledge,
   desultorily, or for amusement only.
   [1913 Webster]

         The true poet is not an eccentric creature, not a mere
         artist living only for art, not a dreamer or a
         dilettante, sipping the nectar of existence, while he
         keeps aloof from its deeper interests.   --J. C.
                                                  Shairp.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dilettante
    adj 1: showing frivolous or superficial interest; amateurish;
           "his dilettantish efforts at painting" [syn:
           dilettante, dilettantish, dilettanteish,
           sciolistic]
    n 1: an amateur who engages in an activity without serious
         intentions and who pretends to have knowledge [syn:
         dabbler, dilettante, sciolist]