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[as-tuh-roid] /ˈæs təˌrɔɪd/
Also called minor planet. Astronomy. any of the thousands of small bodies of from 480 miles (775 km) to less than one mile (1.6 km) in diameter that revolve about the sun in orbits lying mostly between those of Mars and Jupiter.
Zoology. an asteroidean; a starfish.
Origin of asteroid
1795-1805; < Greek asteroeidḗs starry, starlike. See asterisk, -oid
Related forms
asteroidal, adjective
interasteroidal, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the Web for asteroid
Contemporary Examples
Historical Examples
  • The question was, would the Connie try to set his ship down on the asteroid?

    Rip Foster in Ride the Gray Planet Harold Leland Goodwin
  • But the mechanism controlling the asteroid's invisibility was not destroyed.

    The Bluff of the Hawk Anthony Gilmore
  • Now there was only one thin pair of wires stretching between his ship and the drill on the asteroid.

    Anchorite Randall Garrett
  • Anything that kept them from selling an asteroid must be terrible indeed.

  • And they were doing a little target practice with plastic bubbles only a few miles above the asteroid.

    Acid Bath Vaseleos Garson
British Dictionary definitions for asteroid


Also called minor planet, planetoid. any of numerous small celestial bodies that move around the sun mainly between the orbits of Mars and Jupiter. Their diameters range from 930 kilometres (Ceres) to less than one kilometre
Also called asteroidean (ˌæstəˈrɔɪdɪən). any echinoderm of the class Asteroidea; a starfish
of, relating to, or belonging to the class Asteroidea
shaped like a star
Word Origin
C19: from Greek asteroeidēs starlike, from astēr a 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
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Word Origin and History for asteroid

1802, coined probably by German-born English astronomer William Herschel (1738-1822) from Greek asteroeides "star-like," from aster "star" (see astro-) + -eidos "form, shape" (see -oid).

Online Etymology Dictionary, © 2010 Douglas Harper
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asteroid in Science
Any of numerous small, often irregularly shaped rocky bodies that orbit the Sun primarily in the asteroid belt, a region between the orbits of Mars and Jupiter. Asteroids are intermediate in size between planets and meteoroids; the largest asteroid in the asteroid belt is Ceres, approximately 1,000 km (620 mi) in diameter, while the lower limit is variously given in the tens or hundreds of meters. While more than 1,800 asteroids have been cataloged, and as many as a million or more smaller ones may exist, their total mass has been estimated to be less than three percent of the Moon's. Asteroids are thought to be left over from the early formation of the solar system, when planetesimals in a protoplanetary disk were scattered after coming under Jupiter's gravitational influence. The continuing collision of planetesimals that remained between Jupiter and Mars caused many of them to fragment, creating the asteroids that exist today. Also called minor planet, planetoid.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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asteroid in Culture
asteroid [(as-tuh-royd)]

A small planet that revolves around the sun. The largest asteroid is only about six hundred miles in diameter. (See asteroid belt.)

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