[ as-tuh-roid ]
/ ˈæs təˌrɔɪd /
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Astronomy. any of millions of small celestial objects revolving around the sun, often irregularly shaped and having a great range in size, from as small as 6 feet (2 meters) across to about 620 miles (998 kilometers) across: the vast majority of known asteroids exist within the asteroid belt. See also small solar system body.
Zoology. a starfish; an asteroidean.
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Origin of asteroid

First recorded in 1795–1805; from Greek asteroeidḗs “starry, starlike”; see star, -oid


as·ter·oi·dal, adjectivein·ter·as·ter·oi·dal, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use asteroid in a sentence

British Dictionary definitions for asteroid

/ (ˈæstəˌrɔɪd) /

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
adjective Also: asteroidal (ˌæstəˈrɔɪdəl)
of, relating to, or belonging to the class Asteroidea
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

Scientific definitions for asteroid

[ ăstə-roid′ ]

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.

Cultural definitions for 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 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.