off2 [only before noun]
a day, week etc when you are not doing something as well as you usually do:
Brian never usually loses his temper - he must be having an off day.
a period or season which is not as busy as other times of the year:
In the off season, there's hardly anyone staying at the hotel.
3TTC British English
used to talk about a pair of things such as wheels on a car, to mean the one on the right [≠ near]