as·​ter·​oid | \ˈas-tə-ˌrȯid \

Definition of asteroid 

(Entry 1 of 2)

1 : any of the small rocky celestial bodies found especially between the orbits of Mars and Jupiter

2 : starfish



Definition of asteroid (Entry 2 of 2)

1 : resembling a star asteroid bodies in sporotrichosis

2 : of or resembling a starfish

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Other Words from asteroid


asteroidal \ˌas-​tə-​ˈrȯi-​dᵊl \ adjective

Examples of asteroid in a Sentence


Most asteroids are found between Mars and Jupiter.

Recent Examples on the Web: Noun

An asteroid, called 2015 TB145, looks from some angles like a human skull, with deep, dark eye sockets. Temi Adebowale, Popular Mechanics, "This Skull-Shaped Space Rock is Going To Fly By Earth Right After Halloween," 28 Sep. 2018 An asteroid that, in certain light conditions, resembles a human skull, will fly past Earth just after Halloween. James Rogers, Fox News, "Eerie skull-shaped asteroid will zoom past Earth just after Halloween," 28 Sep. 2018 Calculated based on your date, time, and location of birth, the chart reveals the position of the planets, asteroids, stars, and celestial points at your exact moment of arrival. Aliza Kelly Faragher, Allure, "What the Position of Venus in Your Birth Chart Means for You," 31 July 2018 As with methane, there could well be non-biological explanations for the presence of carbon-containing molecules on Mars, such as geologic processes or impacts by asteroids, comet, meteors and interplanetary dust. Marcia Dunn,, "New Mars discoveries in ancient lakebed advance case for possible life," 7 June 2018 These sightings granted scientists the chance to find the fragments of the asteroid on Earth. Joe Pappalardo, Popular Mechanics, "For Just 2nd Time Ever, Meteor Hunters Recover Chunks of Rock They Tracked From Space," 9 July 2018 Oumuamua’s path could not be explained entirely by the gravitational tug of the sun, the planets, the moon, Pluto or any of the 16 largest asteroids in the main belt that lies between the orbits of Mars and Jupiter. Amina Khan,, "'Oumuamua, the mysterious visitor from outside the solar system, is a comet after all," 28 June 2018 The spacecraft will also deploy three rovers that don’t have wheels but can hop around on the surface of the asteroid to conduct probes. Washington Post, "Japan space explorer arrives at asteroid to collect samples," 26 June 2018 About three-quarters of asteroids in the solar system fall into the C-type. Kenneth Chang, New York Times, "Japan’s Hayabusa2 Spacecraft Creeps Up on the Ryugu Asteroid," 25 June 2018

Recent Examples on the Web: Adjective

Last year, a skyscraper-sized asteroid named (441987) 2010 NY65 flew past Earth at about eight times the distance between Earth and the moon. James Rogers, Fox News, "Eerie skull-shaped asteroid will zoom past Earth just after Halloween," 28 Sep. 2018 An international research project from Japan and Australia offers a new potential solution: an ion beam shepherd (IBS), a still-hypothetical contactless approach originally designed for asteroid deflection. David Grossman, Popular Mechanics, "New Space Junk Solution Would Clean Up Debris With Ion Beams," 27 Sep. 2018 The majority of what was recovered from the asteroid impact site is ureilite, a rare type of meteorite with high concentrations of carbon, graphite and diamonds in between grains of silicate. Ashley Strickland, CNN, "These diamonds are from one of our solar system's 'lost planets'," 17 May 2018 Night of the Comet (1984) After an asteroid strikes Earth, the only folks alive or not turned into zombies in Los Angeles (and possibly the world) are two valley girls. Joyce Bautista Ferrari, Marie Claire, "The Best Horror Movies That Aren't Too Scary," 29 Oct. 2018 Caltech’s Konstantin Batygin, for one, does not think the Kuiper Belt objects have enough mass to pull minor planets and asteroid out of their orbit. Jason Daley, Smithsonian, "Is the Mysterious Planet Nine Just a Swarm of Asteroids?," 6 June 2018 These findings are part of a long-standing debate over whether the mass extinction was caused by an asteroid or volcano eruptions on Earth. Sophie Weiner, Popular Mechanics, "Dinosaur-Killing Asteroid May Have Also Triggered Undersea Volcano Eruptions," 9 Feb. 2018 Earth is going to come in close contact with an asteroid Tuesday the size of a city block. Emily Price, Fortune, "An Asteroid the Size of a City Block Will Fly Close to Earth Today," 15 May 2018 Dermott and his colleagues analyzed asteroids in that region that weren't previously categorized into any asteroid families. Fox News, "Meteorites on Earth may come from just a handful of early lost worlds," 4 July 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'asteroid.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of asteroid


1802, in the meaning defined at sense 1


1824, in the meaning defined at sense 1

History and Etymology for asteroid


Greek asteroeidēs starlike, from aster-, astēr

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Statistics for asteroid

Last Updated

9 Dec 2018

Look-up Popularity

Time Traveler for asteroid

The first known use of asteroid was in 1802

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More Definitions for asteroid



English Language Learners Definition of asteroid

: any one of thousands of small planets that circle around the sun


as·​ter·​oid | \ˈa-stə-ˌrȯid \

Kids Definition of asteroid

: one of thousands of rocky objects that move in orbits mostly between those of Mars and Jupiter and have diameters from a fraction of a mile to nearly 500 miles (800 kilometers)


as·​ter·​oid | \ˈas-tə-ˌrȯid \

Medical Definition of asteroid 

: resembling a star

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More from Merriam-Webster on asteroid

Rhyming Dictionary: Words that rhyme with asteroid

Spanish Central: Translation of asteroid

Nglish: Translation of asteroid for Spanish Speakers

Britannica English: Translation of asteroid for Arabic Speakers Encyclopedia article about asteroid

Comments on asteroid

What made you want to look up asteroid? Please tell us where you read or heard it (including the quote, if possible).


a knickknack or trinket

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