The Collaborative International Dictionary of English v.0.48:

Litchi \Li"tchi`\ (l[=e]"ch[=e]`), n. (Bot.)
   The fruit of a tree native to China (Nephelium Litchi). It
   is nutlike, having a rough but tender shell, containing an
   aromatic pulp, and a single large seed. In the dried fruit
   which is exported the pulp somewhat resembles a raisin in
   color and form. [Written also lichi, and lychee.]
   [1913 Webster]

   2. (Bot.) A genus of East Indian sapindaceous trees
      consisting of a single species (Litchi Chinensis, syn.
      Nephelium Litchi) which bears the litchi nut.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

litchi
    n 1: Chinese tree cultivated especially in Philippines and India
         for its edible fruit; sometimes placed in genus Nephelium
         [syn: litchi, lichee, litchi tree, Litchi
         chinensis, Nephelium litchi]
    2: Chinese fruit having a thin brittle shell enclosing a sweet
       jellylike pulp and a single seed; often dried [syn: litchi,
       litchi nut, litchee, lichi, leechee, lichee,
       lychee]