com·​et ˈkä-mət How to pronounce comet (audio)
: 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
cometary adjective
cometic adjective

Example Sentences

Recent Examples on the Web Images of the impact showed tons of debris ejected in all directions, ultimately creating an almost comet-like 10,000-km dust trail behind Dimorphos. Tim Fernholz, Quartz, 12 Oct. 2022 The image shows an expanding, comet-like tail more than 6,000 miles long, consisting of dust and other material spewed from the impact crater. Marcia Dunn, Orlando Sentinel, 7 Oct. 2022 The comet, officially known as 73P/Schwassmann-Wachmann, or SW3, was discovered in 1930 by German observers Arnold Schwassmann and Arno Arthur Wachman. Katie Hunt, CNN, 31 May 2022 Halley’s comet was discovered by Edmund Halley in 1705, but it is believed to have been recognized for millenniums. Doyle Rice, USA TODAY, 3 May 2022 The comet was discovered in 1862 independently by both Lewis Swift and Horace Tuttle. Julia Musto, Fox News, 17 Mar. 2022 Don't Look Up stars Leonardo DiCaprio and Jennifer Lawrences as astronomers trying to alert officials — like U.S. president Meryl Streep — that a comet is headed toward Earth with a deadly outcome for the planet. Benjamin Vanhoose,, 6 Jan. 2022 The other 1998 asteroid movie wherein a comet is discovered to be on a collision course with Earth, as the human race prepares for doomsday. Ben Flanagan |, al, 25 Nov. 2021 In 2016, Meech and colleagues reported the discovery of an unusual long-period comet that was dark and lacked a bright tail of vaporized ice. Byeric Hand,, 5 Oct. 2022 See More

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.

Word History


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

First Known Use

before the 12th century, in the meaning defined above

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

Dictionary Entries Near comet

Cite this Entry

“Comet.” Dictionary, Merriam-Webster, Accessed 30 Nov. 2022.

Kids Definition



com·​et ˈkäm-ət How to pronounce comet (audio)
: a bright heavenly body that develops a cloudy tail as it moves closer to the sun in its orbit

More from Merriam-Webster on comet

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