A wanderer that orbits a star — world enough to hold seasons; the sky's larger bodies, each with its own weather.
Greek πλανήτης (planētēs, a wanderer), from πλανᾶσθαι (planasthai, to wander, stray); named for the one thing that set them apart from the fixed stars — that they visibly moved.
A body that visibly wanders against the fixed stars, large enough to hold its own weather and its own seasons.