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: Webster's Revised Unabridged Dictionary (1913)