(astronomy, planetology) a planetary-mass object which has either been ejected from its system or was never gravitationally bound to any star or other such object, and that therefore orbits the galaxy directly.

(now chiefly historical) A white witch.

plural of planet wheel

(UK, slang) The Isle of Thanet.

(astronomy) A theoretical ninth planet in the Solar system, the gravitational effects of which would explain the improbable orbital configuration of a group of trans-Neptunian objects that orbit mostly beyond the Kuiper belt.

the planet Mars

(astronomy) A planet which orbits in the habitable zone around a star, where temperatures like those on Earth occur, allowing for the possible existence of liquid water and of life.

The planet Uranus.

Any of the four gas giant planets in the Solar System: Jupiter, Uranus, Saturn, or Neptune.

(astronomy) A hypothetical planet in the Solar system, beyond the currently known outermost planet. (The term was applied to Eris for a short while, when Pluto was still considered the ninth planet.)