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  1. 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.
  2. Zoology. an asteroidean; a starfish.
  1. starlike.

Origin of asteroid

First recorded in 1795–1805, asteroid is from the Greek word asteroeidḗs starry, starlike. See asterisk, -oid
Related formsas·ter·oi·dal, adjectivein·ter·as·ter·oi·dal, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for asteroid


  1. 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
  2. Also called: asteroidean (ˌæstəˈrɔɪdɪən) any echinoderm of the class Asteroidea; a starfish
adjective Also: asteroidal (ˌæstəˈrɔɪdəl)
  1. of, relating to, or belonging to the class Asteroidea
  2. shaped like a star

Word Origin for asteroid

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

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

asteroid in Science


  1. Any of numerous small solar system 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 with diameters that measure between approximately one hundred and several hundred kilometers. 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 © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

asteroid in Culture



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

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.