[nep-toon, -tyoon]
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.

< Neo-Latin Neptunea; see Neptune, -ea Unabridged


[nep-toon, -tyoon]
the ancient Roman god of the sea, identified with the Greek god Poseidon.
the sea or ocean: Neptune's mighty roar.
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. See table under planet ( def 1 ).
a township in E New Jersey. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
Cite This Source Link To Neptune
World English Dictionary
Neptune1 (ˈnɛptjuːn)
Greek counterpart: Poseidon the Roman god of the sea

Neptune2 (ˈnɛptjuːn)
the eighth planet from the sun, having eight 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 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
Cite This Source
Word Origin & History

c.1385, from L. Neptunus, the Roman god of the sea (later identified with Gk. Poseidon), probably from PIE base *(e)nebh- "moist" (cf. L. nebula "fog, mist, cloud;" see nebula). The planet so named was discovered by Galle in 1846. Until the identification of Pluto in 1930,
it was the most distant planet known. Neptunian (1794) in the geological sense refers to actions of water; usually opposed to volcanic or plutonic.
Online Etymology Dictionary, © 2010 Douglas Harper
Cite This Source
American Heritage
Science Dictionary
Neptune   (něp'tn')  Pronunciation Key 
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, making Neptune the farthest planet from the Sun during that period. 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. See Table at solar system.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
Cite This Source
American Heritage
Cultural Dictionary

[Greek name Poseidon]

The Roman and Greek god who ruled the sea.

Note: Neptune is frequently portrayed as a bearded giant with a fish's scaly tail, holding a large three-pronged spear, or trident.
Note: The eighth planet from the sun (the Earth is third) is named Neptune.

Neptune definition

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.”)

Note: 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.
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
Cite This Source
Computing Dictionary

Neptune definition

A hypertext system for computer assisted software engineering, developed at Tektronix.

The Free On-line Dictionary of Computing, © Denis Howe 2010
Cite This Source
Copyright © 2014, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature