Is the usage (someone) is off for lunch correct?
I think the preceding usage is right but I am not pretty sure.
Yes, very informal, found mainly in speech/ tweets/ blogs.
Off for lunch = out to lunch.
Joe Watson is off for Lunch with the family. via @aryjoecreatives.
… during the period that the employee is off for lunch that they …
… When the group is having a coffee break or it is off for lunch in the foyer, …
… while the camera crew is breaking or if EVERYONE is off for lunch.
Note the other errors of grammar, spelling and style showing that it is casual writing.
~442,000 results on GoogleSearch.
Remember that the other expression out to lunch is an idiom that has other connotations as well, and should be used with care!
While off for lunch is not idiomatic in the same way out to lunch is, I can certainly be off for lunch if I am on at other times:
He works a modified schedule. He's on call from 10 to 2, then off for lunch from 2 to 3, then back on from 3 to 7.
I could also be off to lunch if I'm leaving for lunch.
I just need to finish this report, then it's off to lunch with my girlfriend.
Off for lunch is correct. Out at lunch is also correct. Out to lunch, not so much. Out to lunch doesn't mean that a person's having a lunch, instead it means, quoting:
a person who simply doesn't know something isn't out to lunch. Being out to lunch requires that you not know something, that you don't know you don't know it, and that you don't make any attempts to understand it (probably because you don't know you don't understand).
Basically, an out to lunch person is someone that's not paying attention.