ˌoff-ˈduty adjective
if someone such as a policeman, nurse, or soldier is off-duty, they are not working:
an off-duty guard
I shall be off-duty on Thursday.

[TahlilGaran] Dictionary of Contemporary English ▲

off duty
not working.
She goes off duty at midnight.

The police officer was charged with robbing Castillo while he was off duty.

Usage notes: usually said about soldiers, police, medical workers, and people who work a scheduled period of time

[TahlilGaran] English Idioms Dictionary ▲

off duty
to be not working
The police officer was off duty when he saw the bank robbery.

[TahlilGaran] English Idioms Dictionary ▲

off duty
adj. Not supposed to be at work; having free time; not working.
Sailors like to go sight-seeing, when they are off duty in a foreign port.
It seems that all the taxis in New York are off duty whenever it rains.
■ Often used with hyphens, before a noun.
The bank robber was captured by an off-duty policeman.
Antonym: ON DUTY.

[TahlilGaran] English Idioms Dictionary ▲