Source : Webster's Revised Unabridged Dictionary (1913)

Longan \Lon"gan\, n. (Bot.)
   A pulpy fruit related to the litchi, and produced by an
   evergreen East Indian tree ({Nephelium Longan}).

Source : WordNet®

longan
     n : tree of southeastern Asia to Australia grown primarily for
         its sweet edible fruit resembling litchi nuts; sometimes
         placed in genera Euphoria or Nephelium [syn: {lungen}, {longanberry},
          {Dimocarpus longan}, {Euphoria litchi}, {Nephelium
         longana}]