The Collaborative International Dictionary of English v.0.48:

Easter lily \Eas"ter lil`y\ (Bot.)
   Any one of various lilies or lilylike flowers which bloom
   about Easter; specif.:
   (a) The common white lily (Lilium candidum), called also
       Annunciation lily.
   (b) The larger white lily (Lilium longiflorum eximium, syn.
       L. Harrisii) called also Bermuda lily.
   (c) The daffodil (Narcissus Pseudo-Narcissus).
   (d) The Atamasco lily.
       [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

Easter lily
    n 1: tall lily have large white trumpet-shaped flowers that
         bloom in the spring [syn: Easter lily, Bermuda lily,
         white trumpet lily, Lilium longiflorum]