of, relating to, or resembling a planet or the planets.
wandering; erratic.
terrestrial; global.
Machinery. noting or pertaining to an epicyclic gear train in which a sun gear is linked to one or more planet gears also engaging with an encircling ring gear.


Machinery. a planetary gear train.

Origin of planetary

From the Latin word planētārius, dating back to 1585–95. See planet, -ary
Related formsnon·plan·e·tar·y, adjective
Can be confusedplanetary plenary plentiful plenitude Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for planetary

Contemporary Examples of planetary

Historical Examples of planetary

  • You get in touch with planetary health services immediately!

    Pariah Planet

    Murray Leinster

  • The planetary president, Wilcox, is in alliance with the war party.

    The Martian Cabal

    Roman Frederick Starzl

  • The planetary rulers had taken no chances of tampering with their propaganda.

    The Martian Cabal

    Roman Frederick Starzl

  • I see sir, that you are most apt in the calculation of the planetary hours.

    The Memoires of Casanova, Complete

    Jacques Casanova de Seingalt

  • But there are hundreds of planetary bodies now known that were then not known.

British Dictionary definitions for planetary



of or relating to a planet
mundane; terrestrial
wandering or erratic
astrology under the influence of one of the planets
(of a gear, esp an epicyclic gear) having an axis that rotates around that of another gear
(of an electron) having an orbit around the nucleus of an atom

noun plural -taries

a train of planetary gears
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

Word Origin and History for planetary

1590s; see planet + -ary. Probably from Late Latin planetarius "pertaining to a planet or planets," but this is attested only as "an astrologer." Planetary nebula, so called for its shape, attested from 1785.

Online Etymology Dictionary, © 2010 Douglas Harper

planetary in Science



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.
Related formsplanetary adjective
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.