Also called major planet. any of the eight large heavenly bodies revolving about the sun and shining by reflected light: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, or Neptune, in the order of their proximity to the sun. Until 2006, Pluto was classified as a planet ninth in order from the sun; it has been reclassified as a dwarf planet.
a similar body revolving about a star other than the sun.
(formerly) a celestial body moving in the sky, as distinguished from a fixed star, applied also to the sun and moon.
Astrology. the sun, moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, or Pluto: considered sources of energy or consciousness in the interpretation of horoscopes.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
How to use planet in a sentence
Lakes on Titan are full of methane, and the chemical is a major component of the giant planets Jupiter, Neptune, and so forth.
Orion represents the first step towards human exploration of other planets, like Mars.
As such, they allow us a peek at the chemistry before the planets and moons evolved into what we know them as today.
The combination of those gaps and the young age of HL Tauri suggest planets may form more quickly than astronomers think.
By contrast, the interior of big planets like Jupiter still hold some mysteries, such as whether they have rocky cores.
All the eight planets added together only make one-seven-hundredth part of his weight.God and my Neighbour | Robert Blatchford
This immense and magnificent globe diffuses heat and light to all the other planets.God and my Neighbour | Robert Blatchford
The celebrated Kepler discovered his canon for the periodical motion of the planets.The Every Day Book of History and Chronology | Joel Munsell
But this term would have no mnemonic significance to one who knows the word Mars as meaning only one of the planets.Assimilative Memory | Marcus Dwight Larrowe (AKA Prof. A. Loisette)
In the nine differently colored circular tracks, rolled little globes representing the planets.Fee of the Frontier | Horace Brown Fyfe
British Dictionary definitions for planet
Also called: major planet any of the eight celestial bodies, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune, that revolve around the sun in elliptical orbits and are illuminated by light from the sun
Also called: extrasolar planet any other celestial body revolving around a star, illuminated by light from that star
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
Scientific definitions for planet
In the traditional model of solar systems, a celestial body larger than an asteroid or comet, illuminated by light from a star, such as the Sun, around which it revolves.
A celestial body that orbits the Sun, has sufficient mass to assume nearly a round shape, clears out dust and debris from the neighborhood around its orbit, and is not a satellite of another planet. The eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto was considered to be a planet until its reclassification in 2006 as a dwarf planet. A planetlike body with more than about ten times the mass of Jupiter would be considered a brown dwarf rather than a planet. See also extrasolar planet inner planet outer planet.
- planetary adjective
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Cultural definitions for planet
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.