(astronomy) The study of planets, planetary systems and the solar system.

(astronomy) A world-like planetoid of the Solar system, that is smaller than the classical planets. More specifically, any astronomical body which has a geology defined by hydrostatic equilibrium (and thus has taken the shape a body of water would take, as opposed to a small Solar System body), orbits the Sun (as opposed to a moon), and does not gravitationally dominate other bodies near its orbit (as opposed to a classical planet or, in IAU usage, as opposed to a planet).

(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.)

plural of planer

Someone who helps protect the environment.

(astronomy) Any of many small, solid astronomical objects that orbit a star and form protoplanets through mutual gravitational attraction.

(astronomy) Being or relating to one of these astronomical objects.

Synonym of exoplanet

As much, or as many, as a plane can carry

plural of planeload