Earth; the third planet in the Solar System

(astronomy, celestial mechanics) An imaginary celestial body (corresponding to another, real, orbiting one) which orbits with constant speed along an auxiliary circle (a circle which shares a diameter with the major axis of the elliptical orbit of the corresponding real celestial body), such that its position coincides with the position of the corresponding, real celestial body when that body passes through periapsis.

A gear wheel that revolves around the wheel with which it meshes, in an epicyclic train.

plural of planet-ruler

(now chiefly historical) A white witch.

plural of planet wheel

A planet that orbits the Sun beyond the orbit of the Earth and thus shows retrograde motion when viewed from the Earth

A planet that orbits the Sun within the orbit of the Earth, and thus does not show retrograde motion when viewed from Earth

the planet Earth

a silicate planet