The Collaborative International Dictionary of English v.0.48:

Kindness \Kind"ness\, n. [From Kind. a.]
   1. The state or quality of being kind, in any of its various
      senses; manifestation of kind feeling or disposition
      beneficence.
      [1913 Webster]

            I do fear thy nature;
            It is too full o' the milk of human kindness
            To catch the nearest way.             --Shak.
      [1913 Webster]

            Unremembered acts
            Of kindness and of love.              --Wordsworth.
      [1913 Webster]

   2. A kind act; an act of good will; as, to do a great
      kindness.

   Syn: Good will; benignity; grace; tenderness; compassion;
        humanity; clemency; mildness; gentleness; goodness;
        generosity; beneficence; favor.
        [1913 Webster]

WordNet (r) 3.0 (2006):

kindness
    n 1: the quality of being warmhearted and considerate and humane
         and sympathetic [ant: unkindness]
    2: tendency to be kind and forgiving [syn: forgivingness,
       kindness]
    3: a kind act [syn: kindness, benignity]

Moby Thesaurus II by Grady Ward, 1.0:

129 Moby Thesaurus words for "kindness":
   accommodatingness, act of grace, act of kindness, advantageousness,
   affability, agreeableness, aid, amiability, amiableness,
   amicability, amicableness, amity, assistance, auspiciousness,
   benefaction, beneficence, beneficialness, benefit, benevolence,
   benignity, blessing, charitableness, charity, class, clemency,
   cogency, commiseration, compassion, complaisance, compliance,
   condolence, condonation, congeniality, consideration, cordiality,
   courtesy, decency, desert, dispensation, disregard, excellence,
   expedience, fairness, favor, favorableness, feeling, fineness,
   first-rateness, forbearance, forgiveness, forgivingness,
   friendliness, friendship, generosity, generousness, geniality,
   gentleness, good deed, good offices, good turn, goodliness,
   goodness, grace, graciosity, graciousness, healthiness,
   helpfulness, hospitality, humaneness, humanity, indulgence,
   kind deed, kind offices, kindliness, kindly act, labor of love,
   leniency, long-suffering, longanimity, love, magnanimity, mercy,
   merit, mitigation, mitzvah, neighborlikeness, neighborliness,
   niceness, obligation, obligingness, office, overlooking, pardon,
   pathos, patience, peaceableness, philanthropy, pity, pleasantness,
   profitableness, quality, quarter, relief, reprieve, rewardingness,
   ruth, self-pity, service, skillfulness, sociability, soundness,
   superiority, sympathy, tenderness, thoughtfulness, tolerance, turn,
   understanding, unhostility, unrevengefulness, usefulness, validity,
   value, virtue, virtuousness, warmth, well-affectedness, wholeness,
   worth



The Devil's Dictionary (1881-1906):

KINDNESS, n.  A brief preface to ten volumes of exaction.