(colloquial) A person or thing's normal mode of operation.

Of or relating to operations, especially military operations. / Functioning and ready for use. / Effective or operative. / Determined by means of practical measures.

A person who operates a telephone switchboard. / A person who provides assistance in establishing a connection, or who provides information or takes messages via the telephone.

(computing) Any simple operation, such as addition, multiplication or division, performed on floating point numbers using a single operation.

(military) That portion of a theater of war] which an army passes over in attaining its object.

A company that sells package holidays.

(finance) Negative operating income.

In operation; that operates. / Involved in an operation.

present participle and gerund of operate

Effectual or important. / Functional, in working order. / Having the power of acting; hence, exerting force, physical or moral; active in the production of effects.