asteroid

noun as·ter·oid \ ˈas-tə-ˌrȯid \

Definition of asteroid

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

2 :starfish

—

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

Based on those observations, astronomers now believe MU69 is either one long, skinny, potato-shaped asteroid less than 20 miles in length.

— jason daley, Smithsonian, "New Horizon’s Next Target Is an Oddly Shaped Asteroid," 10 Aug. 2017
These fossils, paleontologist Daniel Ksepka and colleagues report, belong to a new species of prehistoric bird that fluttered around just a few million years after the non-avian dinosaurs were all wiped out by a wayward asteroid.

— brian switek, Scientific American Blog Network, "A Fossil Bird in the Hand...," 2 Aug. 2017
NASA is developing new technologies and capabilities to send astronauts farther than ever before, first to an asteroid in the 2020's, and onward to Mars by the 2030s.

— Courant Community, "Community News For The Valley Edition," 11 July 2017
And the group is developing a plan to stop large asteroids from smashing into us.

— douglas perry, OregonLive.com, "NASA is worried about a huge asteroid hitting Earth, and the space agency has a 'planetary defense' plan," 6 July 2017
The first spacecraft would be used to get a closer look at the comet or asteroid.

— jason daley, Smithsonian, "Geek Out to This Asteroid Day Livestream," 1 July 2017
The release notes that asteroids hit Earth nearly every day, but most are small enough to burn up in the atmosphere.

— dakin andone, CNN, "NASA unveils plan to test asteroid defense technique," 1 July 2017
On average, multiple car-sized asteroids hit the Earth every year.

— ashley strickland, CNN, "Asteroid Day: Monitoring the skies for the next strike," 30 June 2017
Friday is World Asteroid Day -- a day to raise awareness of the hundreds of thousands of asteroids that have the potential to impact Earth.

— CBS News, "Calendar: Week of June 26," 25 June 2017

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

There's going to be a nuclear war after the asteroid hits?

— charles p. pierce, Esquire, "This Week in Voter Suppression," 24 Aug. 2017
Garrison's team developed a tool with a potential for astronauts to utilize for the purpose of scooping minerals from an asteroid surface.

— Howard County Times, "Marriotts Ridge graduate meets astronaut in summer program [West Friendship]," 27 July 2017
But the prevailing theory attributes this extinction to fallout from an asteroid impact.

— jane borden, HWD, "Game of Thrones: There’s a Scientific Reason for Westeros’s Years-Long Winters," 18 July 2017
A giant asteroid crashing into our planet would instantly kill off millions of animals.

— giorgia guglielmi, Science | AAAS, "This is what it would take to kill all life on Earth," 14 July 2017
In the first step toward producing such a spacecraft, the Johns Hopkins Applied Physics Laboratory in Maryland is designing the Double Asteroid Redirection Test (DART).

— douglas perry, OregonLive.com, "NASA is worried about a huge asteroid hitting Earth, and the space agency has a 'planetary defense' plan," 6 July 2017
When the DART spacecraft and the asteroid collide, the spacecraft will be traveling at a staggering 3.7 miles per second.

— dakin andone, CNN, "NASA unveils plan to test asteroid defense technique," 1 July 2017
At this point, however, the rules look pretty clear, and the odds of bucking them are about as good as successfully navigating an asteroid field.

— brian lowry, CNN, "Han Solo movie split shows franchise directors face long odds," 26 June 2017
You’re much more in danger of succumbing to the flu (a one in 63 chance); a car accident (one in 90); a fall (one in 218); a lightning strike (one in 960,000); or even an asteroid (one in 1.6 million).

— william j. kole, The Seattle Times, "Q&A: Afraid of sharks? Flu, asteroids pose far greater risk," 25 June 2017

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)