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1. Current, full-time service in the military. My son is in the army, and I worry so much when he's on active duty.
2. By extension, full-time service in another area of life. I'm still on active duty until I retire at the end of the month.
A perpetrator (of a potential mass shooting) who is actively shooting at people, typically targeting victims in a crowded and confined space. If there is a report of an active shooter, police aim to respond within minutes. The police were quick to respond to the active shooter situation and disarm the attacker.
on active duty
Serving in the military full time, especially being in or prepared to go into battle. My son is in the army, and I worry so much when he's on active duty. After being on active duty for so long, I don't feel fully comfortable being a civilian anymore.
on active duty
in battle or ready to go into battle. (Military.) The soldier was on active duty for ten months. That was a long time to be on active duty.
Full-time service, as in Julian is 81, but he still comes to the office every day and is very much on active duty . This term comes from the military, where it stands in opposition to reserve, which refers to troops still in the military but not actively engaged. It is occasionally transferred to civilian matters as well. [First half of 1800s]