The Collaborative International Dictionary of English v.0.48:

Cruelty \Cru"el*ty\ (-t[y^]), n.; pl. Cruelties (-t[i^]z).
   [OF. cruelt['e], F. cruaut['e], fr. L. crudelitas, fr.
   crudelis. See Cruel.]
   [1913 Webster]
   1. The attribute or quality of being cruel; a disposition to
      give unnecessary pain or suffering to others; inhumanity;
      barbarity.
      [1913 Webster]

            Pierced through the heart with your stern cruelty.
                                                  --Shak.
      [1913 Webster]

   2. A cruel and barbarous deed; inhuman treatment; the act of
      willfully causing unnecessary pain.
      [1913 Webster]

            Cruelties worthy of the dungeons of the Inquisition.

            Macaulay.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cruelty
    n 1: a cruel act; a deliberate infliction of pain and suffering
         [syn: cruelty, inhuman treatment]
    2: feelings of extreme heartlessness [syn: cruelty,
       mercilessness, pitilessness, ruthlessness]
    3: the quality of being cruel and causing tension or annoyance
       [syn: cruelty, cruelness, harshness]