The Collaborative International Dictionary of English v.0.48:

Discretion \Dis*cre"tion\, n. [F. discr['e]tion, L. discretio
   separation, difference, discernment, fr. discernere,
   discretum. See Discreet, Discern.]
   1. Disjunction; separation. [Obs.] --Mede.
      [1913 Webster]

   2. The quality of being discreet; wise conduct and
      management; cautious discernment, especially as to matters
      of propriety and self-control; prudence; circumspection;
      wariness.
      [1913 Webster]

            The better part of valor is discretion. --Shak.
      [1913 Webster]

            The greatest parts without discretion may be fatal
            to their owner.                       --Hume.
      [1913 Webster]

   3. Discrimination.
      [1913 Webster]

            Well spoken, with good accent and good discretion.
                                                  --Shak.
      [1913 Webster]

   4. Freedom to act according to one's own judgment;
      unrestrained exercise of choice or will.
      [1913 Webster]

   At discretion, without conditions or stipulations.
      [1913 Webster] Discretional

WordNet (r) 3.0 (2006):

discretion
    n 1: freedom to act or judge on one's own
    2: knowing how to avoid embarrassment or distress; "the servants
       showed great tact and discretion" [syn: discretion,
       discreetness, circumspection, prudence]
    3: refined taste; tact [syn: delicacy, discretion]
    4: the power of making free choices unconstrained by external
       agencies [syn: free will, discretion]
    5: the trait of judging wisely and objectively; "a man of
       discernment" [syn: discretion, discernment]

Moby Thesaurus II by Grady Ward, 1.0:

183 Moby Thesaurus words for "discretion":
   airtight secrecy, aloofness, alternate choice, alternative, animus,
   anticipation, appetence, appetency, appetite, backwardness,
   bashfulness, blankness, calculation, canniness, care,
   careful consideration, carefulness, caution, cautiousness,
   chilliness, choice, circumspection, circumspectness, close secrecy,
   closeness, coldness, command, common sense, conation, conatus,
   concealment, consideration, constraint, contemplation,
   cool judgment, coolness, crypticness, decision, deliberate stages,
   deliberateness, deliberation, desire, detachment, determination,
   diplomacy, discernment, discreetness, discrimination, disposition,
   distance, envisagement, envisionment, evasion, evasiveness,
   expressionlessness, fancy, farseeingness, farsightedness, forecast,
   foreglance, foregleam, foreglimpse, forehandedness, foreseeing,
   foresight, foresightedness, forethought, free choice,
   free decision, free will, frigidity, frostiness, full consent,
   gingerliness, good judgment, good sense, guardedness, gumption,
   hedge, hedging, heed, heedfulness, hesitation, hiddenness,
   hugger-mugger, hugger-muggery, iciness, impassiveness, impassivity,
   impersonality, inaccessibility, inclination, intention,
   introversion, judgement, judgment, judiciousness, liking,
   longsightedness, looking ahead, lust, mind, mindfulness,
   moderation, modesty, noncontingent free will, objective, option,
   optionality, passion, pawkiness, pleasure, policy, polity,
   possible choice, precaution, prediction, preference, preparation,
   prepublication, preview, prevision, prior consultation, prospect,
   prospection, providence, provision, prudence, prudentialism,
   prudentialness, readiness, reflection, reflectiveness,
   regardfulness, remoteness, repression, reserve, reservedness,
   resolution, restraint, reticence, reticency, retirement, safeness,
   safety first, sagacity, say, say-so, secrecy, secretiveness,
   secretness, sense, sexual desire, slowness to act, solicitude,
   sound judgment, soundness of judgment, standoffishness,
   subduedness, subterfuge, suppression, tact, tentativeness,
   the dark, thoroughness, thoughtfulness, unaffability,
   unapproachability, uncommunicativeness, uncongeniality,
   undemonstrativeness, unexpansiveness, unprecipitateness, velleity,
   volition, weighing, will, will and pleasure, will power, wisdom,
   wish, withdrawal, withdrawnness



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

DISCRETION, crim. law. The ability to know and distinguish between good and
evil; between what is lawful and what is unlawful.
     2. The age at which children are said to have discretion, is not very
accurately ascertained. Under seven years, it seems that no circumstances of
mischievous discretion can be admitted to overthrow the strong presumption
of innocence, which is raised by an age so tender. 1 Hale, P. C. 27, 8; 4
Bl. Coin. 23. Between the ages of seven and fourteen, the infant is, prima
facie, destitute of criminal design, but this presumption diminishes as the
age increases, and even during this interval of youth, may be repelled by
positive evidence of vicious intention; for tenderness of years will not
excuse a maturity in crime, the maxim in these cases being, malitia supplet
aetatem. At fourteen, children are said to have acquired legal discretion. 1
Hale, P. C. 25.



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

DISCRETION, practice. When it is said that something is left to the
discretion of a judge, it signifies that he ought to decide according to the
rules of equity, and the nature of circumstances. Louis. Code, art. 3522,
No. 13; 2 Inst. 50, 298; 4 Serg. & Rawle, 265; 3 Burr. 2539.
     2. The discretion of a judge is said to be the law of tyrants; it is
always unknown; it is different in different men; it is casual, and depends
upon constitution, temper, and passion. In the best, it is oftentimes
caprice; in the worst, it is every vice, folly, and passion, to which human
nature is liable. Optima lex quae minimum relinquit arbitrio judicis:
optimus judex qui minimum sibi. Bac. Aph; 1 Day's Cas.. 80, ii.; 1 Pow.
Mortg. 247, a; 2 Supp. to Ves. Jr. 391; Toull. liv. 3, n. 338; 1 Lill. Ab.
447.
     3. There is a species of discretion which is authorized by express law,
and, without which, justice cannot be administered; for example, an old
offender, a man of much intelligence and cunning, whose talents render him
dangerous to the community, induces a young man of weak intellect to commit
a larceny in company with himself; they are both liable to be punished for
the offence. The law, foreseeing such a case, has provided that the
punishment should be proportioned, so as to do justice, and it has left such
apportionment to the discretion of the judge. It is evident that, without
such discretion, justice could not be administered, for one of these parties
assuredly deserves a much more severe punishment than the other.