Cambridge Dictionaries online Cambridge Dictionaries online

The most popular online dictionary and thesaurus for learners of English

English definition of “planet”


noun [C]  /ˈplæn·ɪt/ us  
earth science an extremely large, round mass of matter, such as Earth or Mars, that moves in a circular path around the sun or another star
adjective [not gradable]  /ˈplæn·əˌter·i/ us  
earth science planetary scientists
(Definition of planet from the Cambridge Academic Content Dictionary © Cambridge University Press)
What is the pronunciation of planet?
Add Cambridge dictionaries to your browser to your website

Definitions of “planet” in other dictionaries

Word of the Day


When birds roost, they go somewhere to rest or sleep.

Word of the Day


Read our blog about how the English language behaves.

Learn More

New Words

Find words and meanings that have just started to be used in English, and let us know what you think of them.

Learn More