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

For now, scientists know of no asteroids or comets heading our way. Marcia Dunn,, "U.S. stepping up Earth's protection from asteroids, comets," 26 June 2018 A year later, Congress authorized NASA to study asteroids and how to deflect them. Nina Burleigh, Newsweek, "We Can Save Ourselves From Earth-Killing Asteroids, But Someone Has to Pay," 11 June 2015 Surface Oncology, a Cambridge startup developing drugs for the treatment of tumors, has named 15 conference rooms for distinctive features on the surface of planets, moons, and asteroids. Jonathan Saltzman,, "Heard in the halls of biotech: I’ll meet you in the Valium room.," 21 Apr. 2018 Over countless cosmic explosions and rebirths, these materials found their way into asteroids and other planetary bodies, which slammed into one another as the cosmic pot stirred. Jonathan Schifman, Popular Mechanics, "The Entire History of Steel," 9 July 2018 Sample return missions to asteroids and a comet were no big deal; cosmic radiation sterilizes those. Adam Rogers, WIRED, "In Search of New Rules to Protect Other Worlds From Earth's Cooties," 2 July 2018 Solar radiation pressure could only cause enough acceleration if 'Oumuamua were exceptionally light, about 1,000 times less dense than a typical asteroid. John Timmer, Ars Technica, "Visitor from another solar system accelerated away from the Sun," 28 June 2018 The Japanese spacecraft Hayabusa 2, which has been on a journey to the Ryugu asteroid since 2014, reached its destination on Wednesday. Lilly Price, USA TODAY, "Japanese spacecraft arrives at 'surprising' diamond-shaped asteroid," 27 June 2018 In the book series, this conflict goes to extremes as a group of belter radicals bombard Earth with asteroids. Andrew Liptak, The Verge, "Now is the perfect time to start watching The Expanse," 24 May 2018

Recent Examples on the Web: Adjective

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 Before arriving at Ceres, Dawn explored the asteroid Vesta. Marcia Dunn, The Seattle Times, "NASA spacecraft sending back close-ups of dwarf planet Ceres," 2 July 2018 After a journey of almost four years and 2 billion miles, a Japanese space probe is closing in on its target, a small asteroid named Ryugu, the Japan Aerospace Exploration Agency (JAXA) said on Sunday. David Freeman /, NBC News, "Japan's Hayabusa 2 space probe snuggles up to odd-looking asteroid," 26 June 2018 After disruption, the asteroid fragments were blown by the wind while falling down, scattering over a wide area. James Rogers, Fox News, "Asteroid discovery: Rare space rock fragment found," 9 July 2018 Before arriving at Ceres, Dawn explored the asteroid Vesta. Marcia Dunn, The Seattle Times, "NASA spacecraft sending back close-ups of dwarf planet Ceres," 2 July 2018 Before arriving at Ceres, Dawn explored the asteroid Vesta. Washington Post, "NASA spacecraft sending back close-ups of dwarf planet Ceres," 2 July 2018 Hayabusa-2 is the successor to Japan’s original Hayabusa spacecraft, which visited the asteroid Itokawa in 2005. Avery Thompson, Popular Mechanics, "Japanese Sample Return Spacecraft Reaches Target Asteroid," 27 June 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

14 Oct 2018

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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 \

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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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).


one that holds something together

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