The Collaborative International Dictionary of English v.0.48:

Nymphaea \Nym*phae"a\, prop. n. [L., the water lily, Gr. ?.]
   (Bot.)
   A genus of aquatic plants having showy flowers (white, blue,
   pink, or yellow, often fragrant), including the white water
   lily and the Egyptia lotus.
   [1913 Webster]

   Note: Recent critics have endeavored to show that this genus
         should be called Castalia, and the name Nymphaea
         transferred to what is now known as Nuphar.
         [1913 Webster]

WordNet (r) 3.0 (2006):

Nymphaea
    n 1: the type genus of the family Nymphaeaceae; any of a variety
         of water lilies [syn: Nymphaea, genus Nymphaea]