com·​et | \ˈkä-mət \

Definition of comet 

: a celestial body that appears as a fuzzy head usually surrounding a bright nucleus, that has a usually highly eccentric orbit, that consists primarily of ice and dust, and that often develops one or more long tails when near the sun

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Other Words from comet

cometary \ ˈkä-​mə-​ˌter-​ē \ adjective
cometic \ kə-​ˈme-​tik , kä-​ \ adjective

Examples of comet in a Sentence

Recent Examples on the Web

And, once built, recent discoveries on comets hint that these have a tendency to assemble themselves in ever more advanced organic structures. Jamie Seidel, Fox News, "This distant planet is one of the best places to search for alien life," 3 Aug. 2018 Dunes have been found on Mars, Venus, Saturn’s moon, Titan, and even a comet. Washington Post, "Archdiocese settles clergy abuse lawsuit," 2 June 2018 Near-Earth objects are comets (cosmic snowballs of frozen gases, rock and dust the size of a small town) and asteroids (basically, space rocks smaller than planets) that pass within 28 miles of Earth’s orbit. Ashley May, USA TODAY, "NASA: Here's the big plan to protect the planet from 'near-Earth objects'," 21 June 2018 Organic molecules are being found in comets and cosmic clouds. Jamie Seidel, Fox News, "Wild new alien theory emerges," 28 June 2018 The compound is stirred into the comet at its formation, a fingerprint of the early planetary system. Nola Taylor Redd, Scientific American, "Interstellar Mystery Object Now Thought to Be a Comet," 27 June 2018 Every year in August, the Swift-Tuttle comet puts on a brilliant show. Brian Resnick, Vox, "Summer is for meteor showers and stargazing. Here’s how to watch.," 22 June 2018 On June 8, 2017, a story published by The Oregonian/OregonLive became the comet that ricocheted 'round the baseball universe and beyond. Ron Richmond For The Oregonian/oregonlive,, "Inside Luke Heimlich's senior season with the Oregon State baseball team," 8 June 2018 The debris left behind by the comet burns up in our atmosphere creating fiery streaks observed in the night sky. Sarah Gray, Fortune, "The 2018 Lyrid Meteor Shower Will Light Up the Sky on Earth Day. Here Are the Best Places to See It," 17 Apr. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'comet.' 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 comet

before the 12th century, in the meaning defined above

History and Etymology for comet

Middle English comete, from Old English cometa, from Latin, from Greek komētēs, literally, long-haired, from koman to wear long hair, from komē hair

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Statistics for comet

Last Updated

15 Nov 2018

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Time Traveler for comet

The first known use of comet was before the 12th century

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More Definitions for comet



English Language Learners Definition of comet

: an object in outer space that develops a long, bright tail when it passes near the sun


com·​et | \ˈkä-mət \

Kids Definition of comet

: a small bright heavenly body that develops a cloudy tail as it moves in an orbit around the sun

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More from Merriam-Webster on comet

Spanish Central: Translation of comet

Nglish: Translation of comet for Spanish Speakers

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

Comments on comet

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


noxious or harmful

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