American English

Definition of operation noun from the Oxford Advanced American Dictionary



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  1. 1[countable] the process of cutting open a part of a person's body in order to remove or repair a damaged part Will I need to have an operation? He underwent a three-hour heart operation. operation (on somebody/something) (to do something) an operation on her lung to remove a tumor operation (on somebody/something) (for something) Doctors performed an emergency operation for appendicitis last night.
  2. organized activity
  3. 2[countable] an organized activity that involves several people doing different things a security operation The police have launched a major operation against drug dealers. the UN peacekeeping operations
  4. business
  5. 3[countable] a business or company involving many parts a huge multinational operation
  6. 4[countable] the activity or work done in an area of business or industry the firm's banking operations overseas
  7. computer
  8. 5[countable, uncountable] an act performed by a machine, especially a computer The whole operation is performed in less than three seconds.
  9. machine/system
  10. 6[uncountable] the way that parts of a machine or a system work; the process of making something work Regular servicing guarantees the smooth operation of the engine. Operation of the device is extremely simple.
  11. military activity
  12. 7[countable, usually plural] military activity He was the officer in charge of operations.
  13. mathematics
  14. 8[countable] a process in which a number or quantity is changed by adding, multiplying, etc.
  15. Idioms
    come into operation
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    to start working; to start having an effect synonym come/enter into force The new rules will come into operation next week.
    in operation
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    working, being used, or having an effect The system has been in operation for six months. Temporary traffic controls are in operation on Route 47.
    put something into operation
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    to make something start working; to start using something It's time to put our plan into operation.
See the Oxford Advanced Learner's Dictionary entry: operation