TO BE ON ANOTHER PLANET


Meaning of TO BE ON ANOTHER PLANET in English

to be on another planet | what ˈplanet is sb on?

( informal , humorous ) used to suggest that sb's ideas are not realistic or practical :

He thinks being a father is easy. What planet is he on?

Oxford Advanced Learner's English Dictionary.      Оксфордский английский словарь для изучающик язык на продвинутом уровне.