/nep"toohn, -tyoohn/ , n.
1. the ancient Roman god of the sea, identified with the Greek god Poseidon.
2. the sea or ocean: Neptune's mighty roar.
3. Astron. the planet eighth in order from the sun, having an equatorial diameter of 30,200 mi. (48,600 km), a mean distance from the sun of 2794.4 million mi. (4497.1 million km), a period of revolution of 164.81 years, and two moons. See table under planet (def. 1).
4. a township in E New Jersey. 28,366.