The noun operation has 11 senses (first 10 from tagged texts)
1. (439) operation -- (a business especially one run on a large scale; "a large-scale farming operation"; "a multinational operation"; "they paid taxes on every stage of the operation"; "they had to consolidate their operations")
2. (276) operation -- (a planned activity involving many people performing various actions; "they organized a rescue operation"; "the biggest police operation in French history"; "running a restaurant is quite an operation"; "consolidate the companies various operations")
3. (117) operation, procedure -- (a process or series of acts especially of a practical or mechanical nature involved in a particular form of work; "the operations in building a house"; "certain machine tool operations")
4. (99) operation -- (the state of being in effect or being operative; "that rule is no longer in operation")
5. (80) operation, surgery, surgical operation, surgical procedure, surgical process -- (a medical procedure involving an incision with instruments; performed to repair damage or arrest disease in a living body; "they will schedule the operation as soon as an operating room is available"; "he died while undergoing surgery")
6. (66) operation, military operation -- (activity by a military or naval force (as a maneuver or campaign); "it was a joint operation of the navy and air force")
7. (19) operation -- ((computer science) data processing in which the result is completely specified by a rule (especially the processing that results from a single instruction); "it can perform millions of operations per second")
8. (10) operation, functioning, performance -- (process or manner of functioning or operating; "the power of its engine determine its operation"; "the plane's operation in high winds"; "they compared the cooking performance of each oven"; "the jet's performance conformed to high standards")
9. (6) mathematical process, mathematical operation, operation -- ((mathematics) calculation by mathematical methods; "the problems at the end of the chapter demonstrated the mathematical processes involved in the derivation"; "they were learning the basic operations of arithmetic")
10. (4) process, cognitive process, mental process, operation, cognitive operation -- ((psychology) the performance of some composite cognitive activity; an operation that affects mental contents; "the process of thinking"; "the cognitive operation of remembering")
11. operation -- (the activity of operating something (a machine or business etc.); "her smooth operation of the vehicle gave us a surprisingly comfortable ride")