The Collaborative International Dictionary of English v.0.48:

operational \operational\ adj.
   1. of or pertaining to operations; as, operational procedure.
      [WordNet 1.5]

   2. Fit or ready for service; available and in working
      condition; as, an operational aircraft. Opposite of
      out-of-service.

   Syn: functional, usable, useable, in order(predicate), in
        working order(predicate), operable.
        [WordNet 1.5]

   3. (Mil.) of or intended for or involved in military
      operations. Opposite of nonoperational.
      [WordNet 1.5]

   4. In force; not expired or annulled; -- of rules or laws.
      [WordNet 1.5]

            de facto apartheid still operational even in the
            `new' African nations                 --Leslie
                                                  Marmon Silko
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

operational
    adj 1: pertaining to a process or series of actions for
           achieving a result; "operational difficulties"; "they
           assumed their operational positions"
    2: fit or ready for use or service; "the toaster was still
       functional even after being dropped"; "the lawnmower is a bit
       rusty but still usable"; "an operational aircraft"; "the
       dishwasher is now in working order" [syn: functional,
       usable, useable, operable, operational]
    3: (military) of or intended for or involved in military
       operations [ant: inactive, nonoperational]
    4: being in effect or operation; "de facto apartheid is still
       operational even in the `new' African nations"- Leslie Marmon
       Silko; "bus service is in operation during the emergency";
       "the company had several operating divisions" [syn:
       operational, in operation(p), operating(a)]

Moby Thesaurus II by Grady Ward, 1.0:

38 Moby Thesaurus words for "operational":
   acting, active, agential, agentival, agentive, at work, behavioral,
   effective, effectual, efficacious, efficient, functional,
   functioning, go, going, going on, in exercise, in force, in hand,
   in operation, in play, in practice, in process, in the works,
   inaction, managerial, manipulational, on foot, on the fire,
   ongoing, operating, operative, performing, practical, practicing,
   running, serving, working