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.
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   2. The quality of being discreet; wise conduct and
      management; cautious discernment, especially as to matters
      of propriety and self-control; prudence; circumspection;
      wariness.
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            The better part of valor is discretion. --Shak.
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            The greatest parts without discretion may be fatal
            to their owner.                       --Hume.
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   3. Discrimination.
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            Well spoken, with good accent and good discretion.
                                                  --Shak.
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   4. Freedom to act according to one's own judgment;
      unrestrained exercise of choice or will.
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   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]