Definition of off-duty in US English:

off-duty

adverb

  • When not engaged in or occupied with one's regular work; away from normal duties.

noun

  • A period off-duty; time spent off-duty.

adjective

  • Of persons: not engaged in or occupied with regular work, not on duty. Also of things, actions, etc.: relating to or suggestive of this state.

Origin

Late 18th century; earliest use found in George Washington (1732–1799), revolutionary army officer and president of the United States of America. From off + duty.