Longman Dictionary of Contemporary English - operation

~ n 1 »MEDICAL« the process of cutting into someone's body to repair or remove a part that is damaged  (a heart bypass operation | She had a bad operation, she had a hysterectomy.) + on/for  (She's going to have an operation on her knee. | perform an operation)  (an operation only the most skilled surgeon could perform) 2 »SET OF ACTIONS« a set of planned actions or activities for a particular purpose  (The whole operation should only take about ten minutes to perform. | a search and rescue operation, expertly performed) 3 »MACHINE/SYSTEM« a) the way the parts of a machine or system work together  (to maintain proper engine operation (=working) | in operation (=working))  (Protective clothing must be worn when the machine is in operation.) b) the process of making a machine or system work  (Operation of the system is automatic.) 4 »BUSINESS« a) a business, company, or organization, especially one with many parts  (Their huge interstate operation reportedly brings in $20 million a year.) b) the work or activities done by a business, organization etc, or the process of doing this work  (Many small businesses fail in the first year of operation. | be in operation)  (Chris's courier service has only been in operation for two months.) 5 »PRINCIPLE/LAW/PLAN ETC« the way something such as a principle, law etc works or has an effect  (the operation of the laws of gravity | in operation)  (a clear example of Murphy's law in operation | come/go into operation (=begin to have an effect))  (The Act will come into operation later this year. | put/bring sth into operation (=make something start to work)) 6 »MILITARY/POLICE ACTION« a planned military or police action, especially one that involves a lot of people  (an espionage operation) 7 »COMPUTERS« technical an action done by a computer  (a multi-tasking machine performing millions of operations per second)