be (living) on another planet

be (living) on another planet

slang To be oblivious to one's surroundings or act strangely. I have no idea what the professor said during today's lecture because I was on another planet the whole time. The millionaire investor always says something wacky in the board meetings—it's like he's on living another planet.

See also: another, on, planet

be on another ˈplanet

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what ˈplanet is somebody on?

(spoken, humorous) used to suggest that somebody’s ideas are not realistic or practical: He can’t really think we’re going to finish the job today, can he? What planet is he on?

See also: another, on, planet