neptune

¹

[ nep-toon, -tyoon ]

noun

1. any whelk of the genus Neptunea, especially N. decemcostata, common along the eastern coast of North America and having a shell with seven to ten raised reddish-brown spiral ridges on a pale beige or yellow background.

Neptune

²

[ nep-toon, -tyoon ]

noun

1. the ancient Roman god of the sea, identified with the Greek god Poseidon.
2. the sea or ocean:

   Neptune's mighty roar.

3. Astronomy. the planet eighth in order from the sun, having an equatorial diameter of 30,200 miles (48,600 km), a mean distance from the sun of 2794.4 million miles (4497.1 million km), a period of revolution of 164.81 years, and two moons.
4. a township in E New Jersey.

Neptune

¹

/ ˈnɛptjuːn /

noun

1. the Roman god of the sea Greek counterpartPoseidon

Neptune

²

/ ˈnɛptjuːn /

noun

1. the eighth planet from the sun, having fourteen known satellites, the largest being Triton and Nereid, and a faint planar system of rings or ring fragments. Mean distance from sun: 4497 million km; period of revolution around sun: 164.8 years; period of rotation: 14 to 16 hours; diameter and mass: 4.0 and 17.2 times that of earth respectively

Neptune

/ nĕp′to̅o̅n′ /

1. The eighth planet from the Sun and the fourth largest, with a diameter almost four times that of Earth. Neptune is a gas giant with a very active weather system, exhibiting extremely long and powerful storms with the fastest winds observed in the solar system. Neptune's axis is tilted 28.8° from the plane of its orbit, and its summer and winter seasons each last 40 years. For a period of 20 years out of every 248, Pluto's highly elliptical orbit crosses within that of Neptune. Neptune has four faint rings and 13 known moons and appears blue due to the absorption of red light by the methane within its atmosphere.
2. See Table at solar system

Neptune

¹

1. In astronomy , a major planet , the eighth planet from the sun . Neptune is named for the Roman god of the sea. Neptune is similar in size and composition to Uranus . It is usually visible only through a telescope and was discovered in the 1840s. For a period ending in 1999, Pluto's orbit took it inside the orbit of neptune . ( See solar system ; see under “Mythology and Folklore.” )

Neptune

²

1. The Roman and Greek god who ruled the sea.

Notes

Some astronomers have suggested that Pluto is not a planet in the usual sense but is an object more like an asteroid , and that Neptune, therefore, is actually the outermost planet.

Word History and Origins

Origin of neptune¹

< New Latin Neptunea; Neptune, -ea

Example Sentences

Imagine a planet the size of Neptune, itself about four times the size of our home planet.

From Salon

The largest Mega Millions prize this year came from a winning $1.128-billion ticket bought at a Rite Aid in Neptune Township, N.J., in March.

From Los Angeles Times

A grand prize of $1.602 billion purchased in a Neptune Beach, Fla., supermarket in August 2023 remains the largest purse in Mega Millions history.

From Los Angeles Times

Taking advantage of a gravitational convergence of four planets that occurs only once every 176 years, the spacecraft soared past Jupiter, Saturn, Uranus and Neptune.

From New York Times

The spacecraft produced the first high-resolution images of the four planets, the rings of Jupiter, Uranus and Neptune, lightning on Jupiter and lava lakes that revealed active volcanoes on Jupiter’s moon Io.

From New York Times

Related Words

• earth