asteroid

[as-tuh-roid]
noun
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.
adjective

Origin:
1795–1805; < Greek asteroeidḗs starry, starlike. See asterisk, -oid

asteroidal, adjective
interasteroidal, adjective
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Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
asteroid (ˈæstəˌrɔɪd)
 
n
1.  minor planet, Also called: 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 any echinoderm of the class Asteroidea; a starfish
 
adj
3.  of, relating to, or belonging to the class Asteroidea
4.  shaped like a star
 
[C19: from Greek asteroeidēs starlike, from astēr a star]

Collins English Dictionary - Complete & Unabridged 10th Edition
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Etymonline
Word Origin & History

asteroid
1802, coined by Herschel from Gk. asteroeides "star-like," from aster "star" (see astro-) + -eidos "form, shape" (see -oid).
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Science Dictionary
asteroid   (ās'tə-roid')  Pronunciation Key 
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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American Heritage
Cultural Dictionary
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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Example sentences
It is the first discovered natural satellite of a larger asteroid.
Then one day a big, bad asteroid came along and wiped out all the dinosaurs.
Astronomers have discovered a unique set of triplets: an asteroid with two
  moons orbiting it.
For the first time, scientists were able to track an asteroid from space to the
  ground and recover pieces of it.
Images for asteroid
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