on duty

noun, plural du·ties.

1. something that one is expected or required to do by moral or legal obligation.
2. the binding or obligatory force of something that is morally or legally right; moral or legal obligation.
3. an action or task required by a person’s position or occupation; function: the duties of a clergyman.
4. the respectful and obedient conduct due a parent, superior, elder, etc.
5. an act or expression of respect.
6. a task or chore that a person is expected to perform: It’s your duty to do the dishes.
7. Military.
   1. an assigned task, occupation, or place of service: He was on radar duty for two years.
   2. the military service required of a citizen by a country: After graduation, he began his duty.
8. Commerce. a specific or ad valorem tax imposed by law on the import or export of goods.
9. a payment, service, etc., imposed and enforceable by law or custom.
10. Chiefly British. tax: income duty.
11. Machinery.
    1. the amount of work done by an engine per unit amount of fuel consumed.
    2. the measure of effectiveness of any machine.
12. Agriculture. the amount of water necessary to provide for the crop in a given area.
13. Baby Talk. bowel movement.

Idioms

14. do duty, to serve the same function; substitute for: bookcases that do duty as room dividers.
15. off duty, not at one’s post or work; at liberty: They spent their days off duty in hiking and fishing.
16. on duty, at one’s post or work; occupied; engaged: He was suspended from the force for being drunk while on duty.

noun plural -ties

1. a task or action that a person is bound to perform for moral or legal reasons
2. respect or obedience due to a superior, older persons, etcfilial duty
3. the force that binds one morally or legally to one’s obligations
4. a government tax, esp on imports
5. British
   1. the quantity or intensity of work for which a machine is designed
   2. a measure of the efficiency of a machine
6. the quantity of water necessary to irrigate an area of land to grow a particular crop
7. 1. a job or service allocated
   2. (as modifier)duty rota
8. do duty for to act as a substitute for
9. off duty not at work
10. on duty at work

n.late 13c., from Anglo-French duete, from Old French deu “due, owed; proper, just,” from Vulgar Latin *debutus, from Latin debitus, past participle of debere “to owe” (see debt). Related: Duties. The sense of “tax or fee on imports, exports, etc.” is from late 15c.; duty-free as a noun is attested from 1958. A tax charged by a government, especially on an import. 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] In addition to the idiom beginning with duty

duty bound

also see:

above and beyond (the call of duty)

active duty

do one’s dutydouble dutyoff dutyon duty.