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]

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "cruelty":
   animality, atrociousness, atrocity, barbarity, barbarousness,
   beastliness, bestiality, bloodiness, bloodlust, bloodthirst,
   bloodthirstiness, bloody-mindedness, brutality, brutalness,
   brutishness, cannibalism, cruelness, ferociousness, ferocity,
   fiendishness, fierceness, flintiness, hardness, harshness,
   heartlessness, inclemency, inexorableness, inhumaneness,
   inhumanity, mercilessness, pitilessness, relentlessness,
   remorselessness, ruthlessness, sadism, sadistic cruelty,
   sanguineousness, savagery, short shrift, tender mercies,
   truculence, uncompassionateness, unfeelingness, unforgivingness,
   unmercifulness, unremorsefulness, unsympatheticness,
   unyieldingness, vandalism, viciousness, violence, wanton cruelty



Bouvier's Law Dictionary, Revised 6th Ed (1856):

CRUELTY. This word has different meanings, as it is applied to different
things. Cruelty may be, 1. From husband towards the wife, or vice versa. 2.
From superior towards inferior, 3. From master towards slave. 4. To animals.
These will be separately considered.
     2.-1. Between husband and wife, those acts which affect the life, the
health, or even the comfort of the party aggrieved, and give a reasonable
apprehension of bodily hurt, are called cruelty. What merely wounds the
feelings is seldom admitted to be cruelty, unless the act be accompanied
with bodily injury, either actual or menaced. Mere austerity of temper,
petulance of manners, rudeness of language, a want of civil attention and
accommodation, even occasional sallies of passion, will not amount to legal
cruelty; 17 Conn. 189; a fortiori, the denial of little indulgences and
particular accommodations, which the delicacy of the world is apt to number
among its necessaries, is not cruelty. The negative descriptions of cruelty
are perhaps the best, under the infinite variety of cases that may occur, by
showing what is not cruelty. 1 Hagg. R. 35; S. C. 4 Eccles. R. 311, 312; 2
Hagg. Suppl. 1; S. C. 4 Eccles. R. 238; 1 McCord's Ch. R. 205; 2 J. J.
Marsh. R. 324; 2 Chit. Pr. 461, 489; Poynt. on Mar. & Div. c. 15, p. 208;
Shelf. on Mar. & Div. 425; 1 Hagg. Cons. R. 37, 458; 2 Ragg. Cons. Rep. 154;
1 Phillim. 111, 132; 8 N H. Rep. 307; 3 Mass. 321; 4 Mass. 487. It is to be
remarked that exhibitions of passion and gusts of anger, which would be
sufficient to create irreconcilable hatred between persons educated and
trained to respect each other's feelings, would, with persons of coarse
manners and habits, have but a momentary effect. An act which towards the
latter would cause but a momentary difference, would with the former, be
excessive cruelty. 1 Briand Med. Leg. 1 ere part. c. 2, art. 3.
     3.-2. Cruelty towards weak and helpless persons takes place where a
party bound to provide for and protect them, either abuses them by whipping
them unnecessarily, or by neglecting to provide for them those necessaries
which their helpless condition requires. To expose a person of tender years,
under a party's care, to the inclemency of the weather; 2 Campb. 650; or to
keep such a child, unable to provide for himself, without adequate food; 1
Leach, 137; Russ. & Ry. 20 or an overseer neglecting to provide food and
medical care to a pauper having urgent and immediate occasion for them;
Russ. & Ry. 46, 47, 48; are examples of this species of cruelty.
     4.-3. By the civil code of Louisiana, art. 192, it is enacted, that
when the master shall be convicted of cruel treatment of his slave, the
judge may pronounce, besides the penalty established for such cases, that
the slave shall be sold at public auction, in order to place him out of the
reach of the power which his master has abused.
     5.-4. Cruelty to animals is an indictable offence. A defendant was
convicted of a misdemeanor for tying the tongue of a calf so near the root
as to prevent its sucking, in order to sell the cow at a greater price, by
giving to her udder the appearance of being full of milk, while affording
the calf all he needed. 6 Rogers, City Hall Rec. 62. A man may be indicted
for cruelly beating his horse. 3 Rogers, City Rec. 191.