The Collaborative International Dictionary of English v.0.48:

Indication \In`di*ca"tion\, n. [L. indicatio: cf. F.
   indication.]
   [1913 Webster]
   1. Act of pointing out or indicating.
      [1913 Webster]

   2. That which serves to indicate or point out; mark; token;
      sign; symptom; evidence.
      [1913 Webster]

            The frequent stops they make in the most convenient
            places are plain indications of their weariness.
                                                  --Addison.
      [1913 Webster]

   3. Discovery made; information. --Bentley.
      [1913 Webster]

   4. Explanation; display. [Obs.] --Bacon.
      [1913 Webster]

   5. (Med.) Any symptom or occurrence in a disease, which
      serves to direct to suitable remedies. Opposite of
      contraindication.

   Syn: Proof; demonstration; sign; token; mark; evidence;
        signal.
        [1913 Webster]

WordNet (r) 3.0 (2006):

indication
    n 1: something that serves to indicate or suggest; "an
         indication of foul play"; "indications of strain";
         "symptoms are the prime indicants of disease" [syn:
         indication, indicant]
    2: the act of indicating or pointing out by name [syn:
       indication, denotation]
    3: (medicine) a reason to prescribe a drug or perform a
       procedure; "the presence of bacterial infection was an
       indication for the use of antibiotics" [ant:
       contraindication]
    4: something (as a course of action) that is indicated as
       expedient or necessary; "there were indications that it was
       time to leave"
    5: a datum about some physical state that is presented to a user
       by a meter or similar instrument; "he could not believe the
       meter reading"; "the barometer gave clear indications of an
       approaching storm" [syn: reading, meter reading,
       indication]

Moby Thesaurus II by Grady Ward, 1.0:

109 Moby Thesaurus words for "indication":
   Christophany, Satanophany, adumbration, angelophany, appearance,
   augury, auspice, avatar, basis for belief, betokening, betokenment,
   body of evidence, broad hint, chain of evidence, clue, clues, cue,
   data, datum, degree, disclosure, dissemination, documentation,
   embodiment, epiphany, evidence, evincement, exhibit, expression,
   fact, facts, foreshadow, foreshadowing, foreshowing, foretoken,
   foretokening, forewarning, gentle hint, gesture, glimmer,
   glimmering, grounds, grounds for belief, hint, implication,
   incarnation, index, indicant, indications, inkling, innuendo,
   insinuation, intimation, item of evidence, kick, look,
   manifestation, mark, material grounds, materialization, measure,
   muniments, mute witness, nod, notion, nudge, omen,
   piece of evidence, pneumatophany, portent, prefiguration,
   preindication, premises, premonitory shiver, premonitory sign,
   premonitory symptom, presignifying, prognostic, prognostication,
   promise, prompt, proof, publication, reading, reason to believe,
   relevant fact, reminder, revelation, scent, shadow, sign, signal,
   significant, signs, soothsay, spoor, suggestion, suspicion,
   symptom, telltale, theophany, token, tokening, track, type,
   warning, whisper, wind, wink