The Collaborative International Dictionary of English v.0.48:

Discreet \Dis*creet"\, a. [Compar. Discreeter; superl.
   Discreetest.] [F. discret, L. discretus separated (whence
   the meaning reserved, prudent), p. p. of discernere. See
   Discern, and cf. Discrete.]
   1. Possessed of discernment, especially in avoiding error or
      evil, and in the adaptation of means to ends; prudent;
      sagacious; judicious; not rash or heedless; cautious.
      [1913 Webster]

            It is the discreet man, not the witty, nor the
            learned, nor the brave, who guides the conversation,
            and gives measures to society.        --Addison.
      [1913 Webster]

            Satire 's my weapon, but I 'm too discreet
            To run amuck, and tilt at all I meet. --Pope.
      [1913 Webster]

            The sea is silent, the sea is discreet.
                                                  --Longfellow.
      [1913 Webster]

   2. Differing; distinct. [Obs.] --Spenser. -- Dis*creet"ly,
      adv. -- Dis*creet"ness, n. Discrepance

WordNet (r) 3.0 (2006):

discreetness
    n 1: knowing how to avoid embarrassment or distress; "the
         servants showed great tact and discretion" [syn:
         discretion, discreetness, circumspection, prudence]
    2: subtly skillful handling of a situation [syn: delicacy,
       diplomacy, discreetness, finesse]