WordReference Random House Learner's Dictionary of American English © 2025
op•er•a•tion /ˌɑpəˈreɪʃən/USA pronunciation
n.
WordReference Random House Unabridged Dictionary of American English © 2025- [countable] an act, instance, process, or manner of working.
- the state of being operative:[uncountable]a rule no longer in operation.
- the using of force, power, or influence;
agency:[uncountable]the operation of alcohol on the brain. - a process of a practical or mechanical nature:[countable]a delicate operation in watchmaking.
- a business transaction:[countable]a shady operation.
- [countable] a business, esp. one run on a large scale.
- Surgery[countable] a medical procedure of cutting open the body to restore or improve the health of a patient, as by removing a diseased part.
- Mathematics[countable] a mathematical process, as addition or multiplication.
op•er•a•tion
(op′ə rā′shən),USA pronunciation n.
- an act or instance, process, or manner of functioning or operating.
- the state of being operative (usually prec. by in or into):a rule no longer in operation.
- the power to act;
efficacy, influence, or force. - the exertion of force, power, or influence;
agency:the operation of alcohol on the mind. - a process of a practical or mechanical nature in some form of work or production:a delicate operation in watchmaking.
- a course or procedure of productive or industrial activity:building operations.
- a particular process or course:mental operations.
- a business transaction, esp. one of a speculative nature;
deal:a shady operation. - a business, esp. one run on a large scale:a multinational operation.
- Surgerya procedure aimed at restoring or improving the health of a patient, as by correcting a malformation, removing diseased parts, implanting new parts, etc.
- Mathematics
- a mathematical process, as addition, multiplication, or differentiation.
- the action of applying a mathematical process to a quantity or quantities.
- Military
- a campaign, mission, maneuver, or action.
- Usually, operations. the conduct of a campaign, mission, etc.
- Military operations, a headquarters, office, or place from which a military campaign, air traffic to and from an airfield, or any of various other activities, is planned, conducted, and controlled.
- Military operations, the people who work at such a headquarters.
- Latin operātiōn- (stem of operātiō), equivalent. to operāt(us) (see operate) + -iōn- -ion
- Middle English operacioun 1350–1400
'base of operations' also found in these entries (note: many are not synonyms or translations):