Definitions for planetˈplæn ɪt

Random House Webster's College Dictionary

plan•etˈplæn ɪt(n.)

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 moving celestial body, as distinguished from a fixed star, applied also to the sun and moon.
Category: Astronomy
Astrol.any celestial body regarded as exerting an influence on human affairs.
(often cap.) the planet Earth considered as a single ecosystem.
Category: Astronomy, Common Vocabulary

Origin of planet:

1250–1300; ME planete (< OF planète) < LL planētae < Gk (astéres) planḗtai lit., wandering (stars)

Princeton's WordNet

planet, major planet(noun)
(astronomy) any of the nine large celestial bodies in the solar system that revolve around the sun and shine by reflected light; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto in order of their proximity to the sun; viewed from the constellation Hercules, all the planets rotate around the sun in a counterclockwise direction
satellite, planet(noun)
a person who follows or serves another
planet(noun)
any celestial body (other than comets or satellites) that revolves around a star

Kernerman English Learner's Dictionary

planet(noun)ˈplæn ɪt
a large object in space that travels around a star
the eight planets in our solar system; exploring the planet Mars

Wiktionary

planet(Noun)
Each of the seven major bodies which move relative to the fixed stars in the night skyu2014the Moon, Mercury, Venus, the Sun, Mars, Jupiter and Saturn.
planet(Noun)
A body which orbits the Sun directly and is massive enough to be in hydrostatic equilibrium (effectively meaning a spheroid) and to dominate its orbit; specifically, the eight major bodies of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. (Pluto was considered a planet until 2006 and has now been reclassified as a dwarf planet.)
planet(Noun)
A large body which directly orbits any star (or star cluster) but which has not attained nuclear fusion.

Origin: From planete, from planeta, from planeta, planetes, from variant of , from πλανάω, of unknown origin. Perhaps from a pel-, cognate with palor, flana, flanta. More at flaunt.

Webster Dictionary

Planet(noun)
a celestial body which revolves about the sun in an orbit of a moderate degree of eccentricity. It is distinguished from a comet by the absence of a coma, and by having a less eccentric orbit. See Solar system
Planet(noun)
a star, as influencing the fate of a men

The Roycroft Dictionary

planet
A planet is a large body of matter entirely surrounded by a void, as distinguished from a clergyman, who is a large void entirely surrounded by matter.