/ ˈplænɪt; NAmE / noun
1.
[ C ] a large round object in space that moves around a star (such as the sun) and receives light from it :
the planets of our solar system
the planet Earth / Venus / Mars
2.
the planet [ sing. ] used to mean 'the world', especially when talking about the environment :
the battle to save the planet
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IDIOMS
- to be on another planet | what planet is sb on?
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WORD ORIGIN
Middle English : from Old French planete , from late Latin planeta , planetes , from Greek planētēs wanderer, planet, from planan wander.