asteroid

noun as·ter·oid \ ˈas-tə-ˌrȯid \

Updated on: 17 Apr 2018

Definition of asteroid

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

2 : starfish

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asteroidal

play \ˌas-tə-ˈrȯi-dᵊl\ adjective

See asteroid defined for English-language learners

See asteroid defined for kids

Examples of asteroid in a Sentence

Most asteroids are found between Mars and Jupiter.

Recent Examples of asteroid from the Web

Midway through season 2, the substance hijacked an asteroid and crashed it onto Venus, where the protomolecule began building… something.

— andrew liptak, The Verge, "Syfy’s The Expanse is back: here’s what you need to know to get caught up," 12 Apr. 2018
But, perhaps most fittingly, the International Astronomical Union recently named an asteroid after her.

— sarah scoles, WIRED, "The Woman Who Knows Everything About the Universe," 4 Apr. 2018
And the asteroid is not big enough to send us the way of the dinosaurs.

— the washington post, OregonLive.com, "There's a small chance an asteroid will smack into Earth in 2135; NASA is working on a plan," 21 Mar. 2018
And the asteroid is not big enough to send us the way of the dinosaurs.

— author: cleve r. wootson jr., Anchorage Daily News, "There’s a small chance an asteroid will smack into Earth in 2135; NASA is working on a plan," 20 Mar. 2018
The team’s computer simulations suggest that up to 36% of binary stars can eject asteroids.

— sid perkins, Science | AAAS, "Mysterious asteroid that visited us from beyond our solar system probably came from a place with two stars," 19 Mar. 2018
And her meteorite studies earned her a similar honor in 1991, when the International Astronomical Union named an asteroid for her.

— richard sandomir, New York Times, "Ursula Marvin, Geologist of the Extraterrestrial, Dies at 96," 9 Mar. 2018
Paul Chodas, manager of the Center for Near-Earth Object Studies at NASA, said asteroids the size of 2018 CB do not often approach this close to our planet.

— deborah netburn, latimes.com, "Earthlings, get ready for a close encounter with an asteroid," 9 Feb. 2018
The main goal of OSIRIS-REx is to return samples from Bennu, an asteroid as big as the Empire State Building.

— katherine kornei, Science | AAAS, "Asteroid-bound spacecraft finds signs of life—on Earth," 26 Mar. 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.

Origin and Etymology of asteroid

Greek asteroeidēs starlike, from aster-, astēr

NEW! Time Traveler

First Known Use: 1802

See Words from the same year

Other Astronomy Terms

gibbous, nadir, nebulous, penumbra, retrograde, sidereal, syzygy, wane, wax, zenith

asteroid

adjective

Definition of asteroid

1 : resembling a star

asteroid bodies in sporotrichosis

2 : of or resembling a starfish

Recent Examples of asteroid from the Web

Kite, for example, suggests that nutrients might come from surprising sources such as asteroid impacts.

— shannon hall, Scientific American, "Are Water Worlds Habitable?," 5 Apr. 2018
For January’s Quadrantids — named for an extinct constellation Quadrans Muralis in the late 18th century — astronomers believe the parent object is asteroid (196256) 2003 EH1, which may have been a comet seen in Asia about 500 years ago.

— blaine friedlander, Washington Post, "The New Year supermoon was glorious, but it will dull the upcoming Quadrantid meteor shower. (Photos)," 2 Jan. 2018
Others prefer the idea of a more sudden mechanism such as a geologic upheaval from planet-scale volcanic eruptions or Earth-shaking asteroid impacts.

— nola taylor redd, Scientific American, "Primeval Salt Shakes Up Ideas on How the Atmosphere Got Its Oxygen," 22 Mar. 2018
Even an asteroid impact is no match for the resilient, microscopic species.

— doyle rice, USA TODAY, "New species of tardigrade, world's most indestructible creature, discovered in parking lot in Japan," 1 Mar. 2018
In response to several questions, asteroid 2002 AJ129 will safely pass Earth on Feb. 4.

— leada gore, AL.com, "'Potentially hazardous' asteroid 2002 AJ129 to soar past Earth Super Bowl Sunday," 25 Jan. 2018
The aftermath of the asteroid impact is the large scale reason for both.

— brian switek, Smithsonian, "What Doomed the Pterosaurs?," 14 Mar. 2018
Between these paragraphs, the Mail inserts occasional reminders that asteroid 2002 AJ129 will not hit Earth, according to NASA.

— avi selk, Washington Post, "Let’s talk about the big scary asteroid that’s NOT going to hit Earth," 21 Jan. 2018
The last significant asteroid event was one that no one saw coming.

— nina burleigh, Newsweek, "We Can Save Ourselves From Earth-Killing Asteroids, But Someone Has to Pay," 11 June 2015

First Known Use of asteroid

1824

ASTEROID Defined for English Language Learners

asteroid

noun

Definition of asteroid for English Language Learners

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

ASTEROID Defined for Kids

asteroid

noun as·ter·oid \ ˈa-stə-ˌrȯid \

Definition of asteroid for Students

: 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)