planet

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. In the traditional model of solar systems, a celestial body larger than an asteroid or comet, illuminated by light from a star, such as the sun, around which it revolves.
2. n. A celestial body that orbits the sun, has sufficient mass to assume nearly a round shape, clears out dust and debris from the neighborhood around its orbit, and is not a satellite of another planet.
3. n. One of the seven celestial bodies, Mercury, Venus, the moon, the sun, Mars, Jupiter, and Saturn, visible to the naked eye and thought by ancient astronomers to revolve in the heavens about a fixed Earth and among fixed stars.
4. n. One of the seven revolving astrological celestial bodies that in conjunction with the stars are believed to influence human affairs and personalities.

Century Dictionary and Cyclopedia

1. n. A star other than a fixed star: a star revolving in an orbit. The sun was formerly considered as a planet, but is now known to be a fixed star. By planet is ordinarily meant a primary planet of the solar system, or body revolving round the sun in a nearly circular orbit. Of these eight are major planets—being, in their order from the sun, Mercury, Venus, the Earth, Mars, Jupiter, Saturn, Uranus, Neptune. There are besides about 300 minor planets known. (See planetoid.) The periodic comets are not regarded as planets. A secondary planet is a satellite, or small body revolving round a primary planet: thus, the moon is a secondary planet. See solar system (under solar), gravitation, Kepler's laws under law), and the names of the major planets.
2. n. Same as planeta

Wiktionary

1. n. Each of the seven major bodies which move relative to the fixed stars in the night sky—the Moon, Mercury, Venus, the Sun, Mars, Jupiter and Saturn.
2. n. Any of various rocky or gaseous spherical bodies orbiting the Sun, specifically the eight major bodies of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. (The Galilean moons, four major asteroids, and the dwarf planet Pluto were formerly included, in the 17th, 19th, and 20th centuries respectively.)
3. n. Any similar spherically shaped or tidally elongated body in orbit around a star or binary star which has cleared the debris out of its orbital path, but which has not attained nuclear fusion.

GNU Webster's 1913

1. n. 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.
2. n. A star, as influencing the fate of a men.

WordNet 3.0

1. n. a person who follows or serves another
2. n. any celestial body (other than comets or satellites) that revolves around a star
3. n. (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