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
Farlex Dictionary of Idioms.

be on another ˈplanet

,

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
Farlex Partner Idioms Dictionary
See also:
  • be on another planet
  • Planet
  • be in another world
  • get (one's) bearings
  • get one's bearings
  • find (one's) bearings
  • find/get your bearings
  • (one's) bearings
  • one's bearings
  • live in a world of (one's) own