Source : Webster's Revised Unabridged Dictionary (1913)

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.

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

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

            The sea is silent, the sea is discreet.
                                                  --Longfellow.

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

Source : WordNet®

discreet
     adj 1: marked by prudence or modesty and wise self-restraint; "his
            trusted discreet aide"; "a discreet, finely wrought
            gold necklace" [ant: {indiscreet}]
     2: unobtrusively perceptive and sympathetic; "a discerning
        editor"; "a discreet silence" [syn: {discerning}]
     3: heedful of potential consequences; "circumspect actions";
        "physicians are now more circumspect about recommending
        its use"; "a discreet investor" [syn: {circumspect}]