asteroid

[as-tuh-roid]

noun

1. 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.

2. Zoology.,  a starfish; an asteroidean.

adjective

1. starlike.

asteroid

/ ˈæstəˌrɔɪd /

noun

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. any echinoderm of the class Asteroidea; a starfish

adjective

1. of, relating to, or belonging to the class Asteroidea

2. shaped like a star

asteroid

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.

2. Also called minor planet planetoid

asteroid

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

Other Word Forms

• asteroidal adjective
• interasteroidal adjective

Word History and Origins

Origin of asteroid¹

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

Word History and Origins

Origin of asteroid¹

C19: from Greek asteroeidēs starlike, from astēr a star

Example Sentences

It also indicates that several kinds of tyrannosaurs may have lived side by side during the final million years before the asteroid impact that ended the age of dinosaurs.

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NEOs include asteroids, comets, and fragments whose orbits bring them close to Earth's path around the sun.

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But the use of low-earth orbit satellites for mobile communications has been criticised by astronomers, who say they pollute the night sky and make it more difficult to spot potential hazards such as asteroids.

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"If we're saying that what is happening right now is like an asteroid hitting Earth, then the problem becomes insurmountable," she said.

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Early results suggested the crater was formed by an asteroid several hundred meters wide about 66 million years ago, but proof remained uncertain.

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Related Words

• earth 
• globe 
• sphere 
• world