com·​et | \ ˈkä-mət How to pronounce comet (audio) \

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 How to pronounce cometary (audio) \ adjective
cometic \ kə-​ˈme-​tik How to pronounce cometic (audio) , kä-​ \ adjective

Examples of comet in a Sentence

Recent Examples on the Web

The fireballs are released from the comet 109P/Swift-Tuttle during its numerous returns to the inner solar system. Christopher Brito, CBS News, "When and where to watch the Perseid meteor shower, which peaks tonight," 12 Aug. 2019 The meteors are tiny specks of dust from the comet Swift-Tuttle, which comes close to Earth every year at this time. Dave Epstein,, "Perseid meteor shower will put on a big celestial show," 10 Aug. 2019 The debris is left behind the comet and creates a giant oval that extends from beyond Pluto to around the sun. Paul Rogers, The Mercury News, "Here comes the best meteor shower of the year: How and when to watch the Perseids," 8 Aug. 2019 The central portion, or nucleus, of Swift-Tuttle is about 16 miles in diameter — making the comet more than two times bigger than the one that scientists believe struck Earth 65 million years ago and killed off the dinosaurs. David Freeman, NBC News, "The Perseid meteor shower should be striking despite the August full moon. Here's how to watch.," 7 Aug. 2019 Delta Aquarid meteors are believed to come from the comet 96P Machholz, which was discovered in 1986. Doyle Rice, USA TODAY, "Look up! The Delta Aquarid meteor shower will light up the night sky Sunday night," 26 July 2019 The Swift-Tuttle comet passes nearest the sun every 133 years, with the most recent approach occurring in 1992. John Meyer, The Know, "The Perseid meteor shower is expected to disappoint this year, but two others may be visible next week," 26 July 2019 The comet had been visited previously by Europe's Rosetta spacecraft, but the new mission would have returned a sample of cometary material to Earth. Eric Berger, Ars Technica, "NASA will fund a revolutionary mission to fly through Titan’s atmosphere," 27 June 2019 More: Perseid meteor shower lights up the sky around the world Saturn, Neptune, Pluto and the comet Chiron were already in retrograde when Uranus entered, according to Newsweek. Emma Keith, Detroit Free Press, "How Uranus' retrograde might affect your next few months," 28 Jan. 2019

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

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6 Sep 2019

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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 How to pronounce comet (audio) \

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).


readily or continually undergoing change

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