plural of planet gear

(engineering) An epicyclic gear; the middle gears in a planetary gear system, spun by the central sun gear

(astronomy, obsolete, archaic) A moon of a planet.

(astronomy, obsolete, archaic) A planet; a natural satellite of a sun.

(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.

Alternative form of Planet 9

(planetology) a planet that flies through interstellar space and has no star to encircle

(science fiction) homeworld

(astronomy) Synonym of carbon planet

(astrology, astronomy) The seven non-fixed astronomical objects in the sky visible to the naked eye that where known in Ancient history