comet

noun

com·​et ˈkä-mət 

: 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

ˈkä-mə-ˌter-ē 

adjective

cometic

kə-ˈme-tik 

kä-

adjective

Examples of comet in a Sentence

Recent Examples on the Web

Though uncommon on our planet, exotic ice may exist in off-Earth environments, from cold and amorphous comet tails to the hot and crushing cores of icy planets. —Shalma Wegsman, Quanta Magazine, 27 Apr. 2026

At the same time, ultraviolet radiation from the sun strips electrons from gas molecules in the comet's coma — a process known as ionization. —Anthony Wood, Space.com, 27 Apr. 2026

In 2020, stargazers flocked to dark sky locations to view the cosmic traveler Neowise, a visible comet then 64 million miles from Earth, with a dusty tail extending more than a million miles. —Ernie Cowan, San Diego Union-Tribune, 26 Apr. 2026

Those processes in a disk, however, can also warm up comets enough to reduce their deuterium levels. —Joseph Howlett, Scientific American, 24 Apr. 2026

Word History

Etymology

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

Rhymes for comet

• grommet
• vomit
• recommit

Kids 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