: 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
Examples of comet in a Sentence
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The fate of a comet that was predicted to pass close to Earth remains a mystery five years after its dramatic breakup in the inner solar system — but some astronomers think a part of it might still be out there.
—
Kiona N. Smith, Space.com, 11 Feb. 2026
Gas from nebulas as well as water from comets and asteroids may have also been a source of Earth’s hydrogen, Hirose added.
—Mindy Weisberger, CNN Money, 10 Feb. 2026
The meteors are fast and sometimes leave persistent trails, but major outbursts aren’t expected until the 2030s when parent comet Tempel-Tuttle returns.
—Jamie Carter, Forbes.com, 25 Jan. 2026
These comets spend most of their time inside the extremely cold Oort cloud and Kuiper Belt, at temperatures averaging -450 degrees Fahrenheit.
—Andrew Paul, Popular Science, 22 Jan. 2026
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Kiona N. Smith, Space.com, 11 Feb. 2026
Gas from nebulas as well as water from comets and asteroids may have also been a source of Earth’s hydrogen, Hirose added.
—Mindy Weisberger, CNN Money, 10 Feb. 2026
The meteors are fast and sometimes leave persistent trails, but major outbursts aren’t expected until the 2030s when parent comet Tempel-Tuttle returns.
—Jamie Carter, Forbes.com, 25 Jan. 2026
These comets spend most of their time inside the extremely cold Oort cloud and Kuiper Belt, at temperatures averaging -450 degrees Fahrenheit.
—Andrew Paul, Popular Science, 22 Jan. 2026
See All Example Sentences for comet
Cite this Entry
“Comet.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/comet. Accessed 14 Feb. 2026.
Copy CitationKids Definition
comet
noun
com·et
ˈkäm-ət 
: a bright heavenly body that develops a cloudy tail as it moves closer to the sun in its orbit
Etymology
Old English cometa "comet," from Latin cometa (same meaning), from Greek komētēs, literally, "long-haired," derived from komē "hair" — related to coma entry 2
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