The Collaborative International Dictionary of English v.0.48:

Lotus \Lo"tus\ (l[=o]"t[u^]s), n. [L. lotus, Gr. lwto`s. Cf.
   Lote.]
   1. (Bot.)
      (a) A name of several kinds of water lilies; as Nelumbium
          speciosum, used in religious ceremonies, anciently in
          Egypt, and to this day in Asia; Nelumbium luteum,
          the American lotus; and Nymph[ae]a Lotus and
          Nymph[ae]a c[ae]rulea, the respectively
          white-flowered and blue-flowered lotus of modern
          Egypt, which, with Nelumbium speciosum, are figured
          on its ancient monuments.
      (b) The lotus of the lotuseaters, probably a tree found in
          Northern Africa, Sicily, Portugal, and Spain
          (Zizyphus Lotus), the fruit of which is mildly
          sweet. It was fabled by the ancients to make strangers
          who ate of it forget their native country, or lose all
          desire to return to it.
      (c) The lote, or nettle tree. See Lote.
      (d) A genus (Lotus) of leguminous plants much resembling
          clover. [Written also lotos.]
          [1913 Webster]

   European lotus, a small tree (Diospyros Lotus) of
      Southern Europe and Asia; also, its rather large bluish
      black berry, which is called also the date plum.
      [1913 Webster]

   2. (Arch.) An ornament much used in Egyptian architecture,
      generally asserted to have been suggested by the Egyptian
      water lily.
      [1913 Webster] Lotus-eater

WordNet (r) 3.0 (2006):

Nymphaea caerulea
    n 1: blue Egyptian lotus: held sacred by the Egyptians [syn:
         blue lotus, Nymphaea caerulea]