The Collaborative International Dictionary of English v.0.48:

Discernment \Dis*cern"ment\, n. [Cf. F. discernement.]
   1. The act of discerning.
      [1913 Webster]

   2. The power or faculty of the mind by which it distinguishes
      one thing from another; power of viewing differences in
      objects, and their relations and tendencies; penetrative
      and discriminate mental vision; acuteness; sagacity;
      insight; as, the errors of youth often proceed from the
      want of discernment.

   Syn: Judgment; acuteness; discrimination; penetration;
        sagacity; insight. -- Discernment, Penetration,
        Discrimination. Discernment is keenness and accuracy
        of mental vision; penetration is the power of seeing
        deeply into a subject in spite of everything that
        intercepts the view; discrimination is a capacity of
        tracing out minute distinctions and the nicest shades of
        thought. A discerning man is not easily misled; one of a
        penetrating mind sees a multitude of things which escape
        others; a discriminating judgment detects the slightest
        differences.
        [1913 Webster]

WordNet (r) 3.0 (2006):

discernment
    n 1: the cognitive condition of someone who understands; "he has
         virtually no understanding of social cause and effect"
         [syn: understanding, apprehension, discernment,
         savvy]
    2: delicate discrimination (especially of aesthetic values);
       "arrogance and lack of taste contributed to his rapid
       success"; "to ask at that particular time was the ultimate in
       bad taste" [syn: taste, appreciation, discernment,
       perceptiveness]
    3: perception of that which is obscure [syn: discernment,
       perceptiveness]
    4: the mental ability to understand and discriminate between
       relations [syn: sagacity, sagaciousness, judgment,
       judgement, discernment]
    5: the trait of judging wisely and objectively; "a man of
       discernment" [syn: discretion, discernment]