out to lunch
- Away eating lunch or for a midday break; especially, away from work or a job.
- She's out to lunch right now, but you may leave her a note.
- (idiomatic, informal) Clueless, inattentive, or careless.
- After he drove with his turn signal on for five miles, I was pretty sure he was out to lunch.
- May also be used as an adverb.