be off
be off {v. phr.}
1. {v.}
To be in error; miscalculate.
The estimator was off by at least 35% on the value of the house.
2. {v.}
To leave.
Jack ate his supper in a hurry and was off without saying goodbye.
3. {adj.}
Cancelled; terminated.
The weather was so bad that we were told that the trip was off.
4. {adj.}
Crazy.
I'm sure Aunt Mathilda is a bit off; no one in her right mind would say such things.
5. {adj.}
Free from work; having vacation time.
Although we were off for the rest of the day, we couldn't go to the beach because it started to rain.
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Source: A Dictionary of American Idioms