on/off duty

off duty

Officially not in the capacity of working during one's normal working day or assigned hours; not on duty. Typically used of doctors, nurses, and police officers. Often hyphenated. Sorry, I'm off duty. You should ask someone at reception. An off-duty police officer leapt into action and managed to apprehend the criminal.
See also: duty, off

on duty

Officially in the capacity of working during one's normal working day or assigned hours. Typically used of doctors, nurses, and police officers. Often hyphenated. I'd love to sit down with you for a drink, but as you can see by the uniform I'm wearing, I'm actually on duty right now. Even though several on-duty police officers were on the scene, no one noticed the burglar stealing the painting.
See also: duty, on
Farlex Dictionary of Idioms.

off duty

not working at one's job. (The opposite of on duty.) I'm sorry, I can't talk to you until I'm off duty. The police officer couldn't help me because he was off duty.
See also: duty, off

on duty

at work; currently doing one's work. (The opposite of off duty.) I can't help you now, but I'll be on duty in about an hour. Who is on duty here? I need some help.
See also: duty, on
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

off duty

see under on duty.
See also: duty, off

on duty

At one's post, at work, as in The new nurse was on duty that evening, or The watchman was fired because he was drunk on duty. [Mid-1600s] The antonym, off duty, means "not engaged in one's work," as in Captain Smith was much more amiable when he was off duty. [Mid-1800s]
See also: duty, on
The American Heritage® Dictionary of Idioms by Christine Ammer.

on/off ˈduty

(of nurses, police officers, etc.) working/not working at a particular time: Who’s on duty today? What time do you go off duty?
See also: duty, off, on
Farlex Partner Idioms Dictionary

off duty

Not engaged in or responsible for assigned work.
See also: duty, off

on duty

Engaged in or responsible for assigned work.
See also: duty, on
American Heritage® Dictionary of the English Language, Fifth Edition.
See also:
  • off duty
  • on duty
  • overtime
  • be working overtime
  • working
  • get on the stick
  • fringe
  • fringe benefit
  • on (one's) own time
  • on own time