MEDICAL TREATMENT›when a doctor cuts someone's body to remove or repair part of it: a heart/lung operationa major/minor operationMy son's got to have an operation.
ORGANIZATION›an organization or business: a large commercial operation
ACTIVITY›an activity that is intended to achieve a particular purpose: a military/peacekeeping operationa joint operation by French and Spanish policean operation to smuggle drugs into Britain
in operation›If a machine or system is in operation, it is working or being used: The new rail link is now in operation.Most of the machines are now back in operation.