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neptune

1 American  
[nep-toon, -tyoon] / ˈnɛp tun, -tyun /

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 American  
[nep-toon, -tyoon] / ˈnɛp tun, -tyun /

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 British  
/ ˈnɛptjuːn /

noun

  1. Greek counterpart: Poseidon.  the Roman god of the sea

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Neptune 2 British  
/ 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

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Neptune Scientific  
/ 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 Cultural  

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

Neptune 2 Cultural  

  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.”)

Discover More

The eighth planet from the sun (the Earth is third) is named Neptune.

Neptune is frequently portrayed as a bearded giant with a fish's scaly tail, holding a large three-pronged spear, or trident.

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.

Etymology

Origin of neptune

< New Latin Neptunea; Neptune, -ea

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

For many years, researchers believed Saturn's precession matched Neptune's, allowing their gravitational interactions to gradually tilt Saturn and make its rings more visible from Earth.

From Science Daily

This subtle difference changes Saturn's precession rate so that it no longer aligns with Neptune's.

From Science Daily

Just after sunset on Saturday, Mercury, Venus, Saturn, and Neptune will appear low in the western sky, close to the horizon.

From BBC

Mercury, Venus, Saturn and Jupiter should be visible to the naked eye but Uranus and Neptune will likely require binoculars or a telescope.

From BBC

Just after sunset, Mercury, Venus, Saturn, and Neptune will appear low in the western sky, close to the horizon.

From BBC

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.