planet

UK: /ˈplænɪt/ US: /ˈplænɪt/ ,(plan′it)

WordReference Random House Learner's Dictionary of American English © 2025

plan•et /ˈplænɪt/   n. [countable]

1. Astronomy
   • any of the nine large heavenly bodies revolving around the sun and shining by reflected light:
     Jupiter is the largest planet in our solar system.
   • a similar body revolving around a star other than the sun.
2. Astronomy the planet Earth:
   [the + ~] Will there be any life on the planet after a nuclear war?

WordReference Random House Unabridged Dictionary of American English © 2025

plan•et  (plan′it), n. 

1. Astronomy
   • Also called major planet. any of the nine large heavenly bodies revolving about the sun and shining by reflected light: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, or Pluto in the order of their proximity to the sun.
   • a similar body revolving about a star other than the sun.
   • (formerly) a celestial body moving in the sky, as distinguished from a fixed star, applied also to the sun and moon.
2. Astrology the sun, moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, or Pluto: considered sources of energy or consciousness in the interpretation of horoscopes.

• Greek (astéres) plané̄tai literally, wandering (stars)
• Late Latin planēta, planētēs (found only in plural planētae)
• Old French planète)
• Middle English planete (1250–1300

Collins Concise English Dictionary © HarperCollins Publishers::

planet / ˈplænɪt/ noun

1. Also called: major planet any of the eight celestial bodies, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune, that revolve around the sun in elliptical orbits and are illuminated by light from the sun
2. Also called: extrasolar planet any other celestial body revolving around a star, illuminated by light from that star
3. any of the planets of the solar system, excluding the earth but including the sun and moon, each thought to rule one or sometimes two signs of the zodiac
   See also house9

Etymology: 12th Century: via Old French from Late Latin planēta, from Greek planētēs wanderer, from planaein to wander