Definition of: Neptune

(nep′tn, -tyn)
1. In Roman mythology, son of Saturn and Ops, god of the sea: identified with the Greek Poseidon.
2. By personification, the ocean.
3. Astron. The eighth planet from the sun, discovered in 1846 by Galle of Berlin. Its mean distance from the sun is 2,793,000,000 miles; period of revolution, about 165 years; diameter, about 27,700 miles. It has two satellites. See PLANET.