The Collaborative International Dictionary of English v.0.48:

Operative \Op"er*a*tive\, a. [Cf.L. operativus, F. op['e]ratif.]
   1. Having the power of acting; hence, exerting force,
      physical or moral; active in the production of effects;
      as, an operative motive; operative laws.
      [1913 Webster]

            It holds in all operative principles. --South.
      [1913 Webster]

   2. Producing the appropriate or designed effect; efficacious;
      effective; as, an operative dose, rule, or penalty.
      [1913 Webster]

   3. (Surg.) Based upon, or consisting of, an operation or
      operations; as, operative surgery.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Operative \Op"er*a*tive\, n.
   1. A skilled worker; an artisan; esp., one who operates a
      machine in a mill or manufactory.
      [1913 Webster]

   2. One who acts as an agent of another, especially a
      detective or spy.
      [PJC]

WordNet (r) 3.0 (2006):

operative
    adj 1: being in force or having or exerting force; "operative
           regulations"; "the major tendencies operative in the
           American political system" [ant: inoperative]
    2: relating to or requiring or amenable to treatment by surgery
       especially as opposed to medicine; "a surgical appendix"; "a
       surgical procedure"; "operative dentistry" [syn: surgical,
       operative] [ant: medical]
    3: effective; producing a desired effect; "the operative word"
    4: (of e.g. a machine) performing or capable of performing; "in
       running (or working) order"; "a functional set of brakes"
       [syn: running(a), operative, functional, working(a)]
    n 1: a person secretly employed in espionage for a government
         [syn: secret agent, intelligence officer, intelligence
         agent, operative]
    2: someone who can be employed as a detective to collect
       information [syn: private detective, PI, private eye,
       private investigator, operative, shamus, sherlock]

Moby Thesaurus II by Grady Ward, 1.0:

134 Moby Thesaurus words for "operative":
   Bow Street runner, CIA man, FBI, FBI agent, Federal, G-man,
   Secret Service, Sherlock Holmes, T-man, accessible, active, actor,
   agent, alive, architect, armipotent, artisan, author,
   authoritative, cloak-and-dagger operative, cogent, conductor,
   counterintelligence agent, counterspy, craftsman, craftswoman,
   creator, detective, doer, double agent, driver, dynamic, effective,
   effectual, efficacious, efficient, employable, employee, energetic,
   engineer, espionage agent, executant, executor, executrix, eye,
   fabricator, fed, forceful, forcible, functional, functionary,
   functioning, go, gumshoe, hand, handler, high-potency,
   high-powered, high-pressure, high-tension, hotel detective,
   house detective, house dick, in force, in power, inquiry agent,
   inside man, intelligence agent, investigator, irresistible,
   laborer, live, machinist, maker, manipulator, mechanic, medium,
   mighty, mighty in battle, military-intelligence man, mover, narc,
   naval-intelligence man, operant, operation, operational, operator,
   performer, perpetrator, pilot, plainclothesman, police detective,
   potent, powerful, practicable, practical, practitioner, prepotent,
   prime mover, private detective, private eye, private investigator,
   producer, puissant, reconnoiterer, revenuer, roustabout, ruling,
   runner, running, scout, secret agent, shamus, sleuth, spotter, spy,
   spy-catcher, steersman, store detective, striking, strong, subject,
   telling, treasury agent, undercover man, usable, valid, vigorous,
   vital, worker, workhand, working, workingman, workman



Bouvier's Law Dictionary, Revised 6th Ed (1856):

OPERATIVE. A workman; one employed to perform labor for another.
     2. This word is used in the bankrupt law of 19th August, 1841, s. 5,
which directs that any person who shall have performed any labor as an
operative in the service of any bankrupt shall be entitled to receive the
full amount of wages due to him for such labor, not exceeding twenty-five
dollars; provided that such labor shall have been performed within six
months next before the bankruptcy of his employer.
     3. Under this act it has been decided that an apprentice who had done
work beyond a task allotted to him by his master, commonly called overwork,
under an agreement on the part of the master to pay for such work, was
entitled as an operative. 1 Penn. Law Journ. 368. See 3 Rob. Adm. R. 237; 2
Cranch, 240 270.