The Collaborative International Dictionary of English v.0.48:

Narcissus \Nar*cis"sus\ (n[aum]r*s[i^]s"s[u^]s), n.; pl.
   Narcissuses. [L. narcissus, and (personified) Narcissus,
   Gr. na`rkissos, Na`rkissos, fr. na`rkh torpor, in allusion to
   the narcotic properties of the flower. Cf. Narcotic.]
   [1913 Webster]
   1. (Bot.) A genus of endogenous bulbous plants with handsome
      flowers, having a cup-shaped crown within the six-lobed
      perianth, and comprising the daffodils and jonquils of
      several kinds.
      [1913 Webster]

   2. (Classical Myth.) (Capitalized)A beautiful youth fabled to
      have been enamored of his own image as seen in a fountain,
      and to have been changed into the flower called Narcissus.
      [1913 Webster]

WordNet (r) 3.0 (2006):

narcissus
    n 1: bulbous plant having erect linear leaves and showy yellow
         or white flowers either solitary or in clusters
    2: (Greek mythology) a beautiful young man who fell in love with
       his own reflection