as·​ter·​oid | \ ˈas-tə-ˌrȯid How to pronounce asteroid (audio) \

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 How to pronounce asteroidal (audio) \ adjective

Examples of asteroid in a Sentence


Most asteroids are found between Mars and Jupiter.

Recent Examples on the Web: Noun

That includes 208 asteroids discovered in the last month alone, and 731 discovered this year so far. Avery Thompson, Popular Mechanics, "Welp, Now We Have 20,000 Potentially Dangerous Asteroids to Worry About," 8 May 2019 Most of those outcasts were rich in icy, cometlike material from the outer solar system rather than rocky asteroids. Nola Taylor Redd, Scientific American, "Interstellar Mystery Object Now Thought to Be a Comet," 27 June 2018 Some new development like photosynthesis, some new surprise like an asteroid or a belch of volcanic carbon, throws a monkey wrench into the world order. Robert M. Thorson, WSJ, "‘Timefulness’ Review: Thinking in Eons," 30 Dec. 2018 The novels play out in a breathtaking alternate world where humanity must establish a foothold off-world after an asteroid devastates Earth. Andrew Liptak, The Verge, "The Lady Astronaut novels are an enthralling alternate history of the space race," 22 Aug. 2018 This unisex garb would be almost utopian, if the poor souls on screen weren’t so busy battling aliens, asteroids or each other. Jacob Gallagher, WSJ, "Who Needs Gender? Why Men and Women Are Dressing Identically," 21 Feb. 2019 First, the astronomers wanted to determine what an interstellar asteroid in our solar system would even look like. Avery Thompson, Popular Mechanics, "There Could Be Hundreds of Interstellar Asteroids Lurking in Our Solar System," 3 Dec. 2018 So, right now, Obama is just another asteroid in Trump's galaxy. Fox News, "Maxine Waters renews calls to impeach President Trump," 11 Sep. 2018 Comets and asteroids that pass within 28 million miles of Earth's orbit are officially classified as near-Earth objects, or NEOs. William Harwood, CBS News, "NASA asteroid-watchers team up on emergency plan with White House, FEMA," 20 June 2018

Recent Examples on the Web: Adjective

So this asteroid-sample mission is about to heat up. Loren Grush, The Verge, "NASA’s asteroid-sampling spacecraft spies its target for the first time," 25 Aug. 2018 Johnson and Melosh said this helps prove the asteroid crash case. Seth Borenstein, The Seattle Times, "Snapshot of extinction: Fossils show day of killer asteroid," 3 Apr. 2019 So if all goes well, two different spacecraft from two different countries may bring back asteroid material for scientists to study. Loren Grush, The Verge, "A Japanese spacecraft just threw two small rovers at an asteroid," 21 Sep. 2018 The asteroid Hayabusa is orbiting, Ryugu, is too far away for a delicate process like this to be controlled from the Earth, so the spacecraft had to handle landing, firing, and sample collection all by itself. Avery Thompson, Popular Mechanics, "Here's How It Looks When a Spacecraft Shoots an Asteroid," 5 Mar. 2019 In the opening chapters of Mary Robinette Kowal’s latest two novels, an asteroid lands just off the US Eastern Seaboard and threatens to drastically change the climate. Andrew Liptak, The Verge, "Our favorite science fiction and fantasy books of 2018," 21 Dec. 2018 Researchers from the University of Southampton set out seven different risks posed by an asteroid collision. Jasper Hamill, Fox News, "7 terrifying ways that asteroids could wipe out life on our planet revealed," 28 June 2018 The National Science and Technology Council released a report Wednesday calling for improved asteroid detection, tracking and deflection. Marcia Dunn,, "U.S. stepping up Earth's protection from asteroids, comets," 26 June 2018 The capsule containing the mission's asteroid samples will come down to Earth a year later, in December 2020. Mike Wall,, "Landing Site on Asteroid Ryugu Chosen for Japan's Hayabusa2 Mission," 23 Aug. 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

13 May 2019

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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 How to pronounce asteroid (audio) \

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 How to pronounce asteroid (audio) \

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 sum of money that is sent as a payment

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