ENGLISH
REFERENCE

comet

n.
US //ˈkɑmət// UK //kˈɒmɪt// comet
  1. 1 astronomy (n.)
    B2 Upper Intermediate Science

    a ball of ice and dust in space that has a long tail of light when it moves near the sun.

    a small solar system body that orbits the sun and, when close enough, displays a visible atmosphere or tail due to the effects of solar radiation.

    Example

    The comet was visible in the night sky for several weeks as it passed the earth.

    Example

    Halley's Comet is perhaps the most famous periodic visitor to our inner solar system, returning to the vicinity of Earth every seventy-five years.

    Usage

    Often used with the verbs 'orbit', 'appear', or 'pass'.

  2. 2 computing (n.)
    C2 Proficiency Technical Computing

    a way for a web server to send information to a browser immediately without waiting for a request.

    a web application model where a long-held HTTP request allows a server to push data to a client browser.

    Example

    The developer used a comet approach to make the chat app update in real time.

    Example

    Before the widespread adoption of WebSockets, Comet was a common technique for achieving low-latency communication between the server and the browser.

    Usage

    Usually treated as an uncountable technical concept or a specific architectural pattern.
    • server push
    • HTTP streaming
Origin

From Middle English comete, partly from Old English comēta and partly from Old French comete, both from Latin comētēs, from Ancient Greek κομήτης (komḗtēs, “longhaired”), short for ἀστὴρ κομήτης ([astēr] komētēs, "longhaired [star])" and referring to the tail of a comet, from κόμη (kómē, “hair”). Compare English faxed star and Latin crīnīta stēlla (“comet”, literally “(long) haired star”).

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

Related words

Last updated June 20, 2026