In various special collocations. a person engaged on secret service, esp. espionage.

Originally and chiefly U.S. An agent employed by a detective agency, secret service, or similar organization; a private investigator. In later use…

An intelligence operative; a secret-service agent. Cf. operative, n. 3b.

(a) chiefly U.S. a person in charge of a railway or (formerly) stagecoach station; (b) a person who works for (a particular branch of) an…