Source : Webster's Revised Unabridged Dictionary (1913)

Neptune \Nep"tune\, n. [L. Neptunus.]
   1. (Rom. Myth.) The son of Saturn and Ops, the god of the
      waters, especially of the sea. He is represented as
      bearing a trident for a scepter.

   2. (Astron.) The remotest known planet of our system,
      discovered -- as a result of the computations of
      Leverrier, of Paris -- by Galle, of Berlin, September 23,
      1846. Its mean distance from the sun is about
      2,775,000,000 miles, and its period of revolution is about
      164,78 years.

Source : WordNet®

Neptune
     n 1: (Roman mythology) god of the sea; counterpart of Greek
          Poseidon
     2: a giant planet with a ring of ice particles; the 8th planet
        from the sun

Source : Free On-Line Dictionary of Computing

Neptune
     
        A hypertext system for computer assisted software engineering,
        developed at Tektronix.