The Collaborative International Dictionary of English v.0.48:

Righteousness \Right"eous*ness\, n. [AS. rihtw[imac]snes.]
   1. The quality or state of being righteous; holiness; purity;
      uprightness; rectitude.
      [1913 Webster]

   Note: Righteousness, as used in Scripture and theology, in
         which it chiefly occurs, is nearly equivalent to
         holiness, comprehending holy principles and affections
         of heart, and conformity of life to the divine law.
         [1913 Webster]

   2. A righteous act, or righteous quality.
      [1913 Webster]

            All our righteousnesses are as filthy rags. --Isa.
                                                  lxiv. 6.
      [1913 Webster]

   3. The act or conduct of one who is righteous.
      [1913 Webster]

            Blessed are they that keep judgment, and he that
            doeth righteousness at all times.     --Ps. cvi. 3.
      [1913 Webster]

   4. (Theol.) The state of being right with God; justification;
      the work of Christ, which is the ground of justification.
      [1913 Webster]

            There are two kinds of Christian righteousness: the
            one without us, which we have by imputation; the
            other in us, which consisteth of faith, hope, and
            charity, and other Christian virtues. --Hooker.
      [1913 Webster]

            Only for the righteousness of Christ imputed to us,
            and received by faith alone.          --Westminster
                                                  Catechism.
      [1913 Webster]

   Syn: Uprightness; holiness; godliness; equity; justice;
        rightfulness; integrity; honesty; faithfulness.
        [1913 Webster]

WordNet (r) 3.0 (2006):

righteousness
    n 1: adhering to moral principles [ant: unrighteousness]

Moby Thesaurus II by Grady Ward, 1.0:

89 Moby Thesaurus words for "righteousness":
   Christianity, Christlikeness, Christliness, angelicalness,
   appropriateness, assured probity, beauty of holiness,
   blamelessness, character, cleanness, correctitude, correctness,
   decencies, decency, decorousness, decorum, erectness,
   estimableness, fairness, fear of God, fitness, fittingness,
   godlikeness, godliness, godly-mindedness, good character, goodness,
   heavenliness, heavenly-mindedness, high ideals, high principles,
   high-mindedness, holiness, holy-mindedness, honesty, honor,
   honorableness, immaculacy, integrity, irreproachability,
   irreproachableness, justice, justness, moral excellence,
   moral rectitude, moral strength, morale, morality, niceness,
   nobility, normality, normativeness, odor of sanctity,
   otherworldliness, principles, probity, properness, proprieties,
   propriety, pureness, pureness of heart, purity, rectitude,
   reputability, respectability, right conduct, rightness, sainthood,
   saintlikeness, saintliness, saintship, sanctitude, sanctity,
   seemliness, seraphicalness, spiritual-mindedness, spirituality,
   stainlessness, suitability, unearthliness, unimpeachability,
   unimpeachableness, unspottedness, unworldliness, uprightness,
   upstandingness, virtue, virtuousness, worthiness



Easton's 1897 Bible Dictionary:

Righteousness
   See JUSTIFICATION.


The Devil's Dictionary (1881-1906):

RIGHTEOUSNESS, n.  A sturdy virtue that was once found among the
Pantidoodles inhabiting the lower part of the peninsula of Oque.  Some
feeble attempts were made by returned missionaries to introduce it
into several European countries, but it appears to have been
imperfectly expounded.  An example of this faulty exposition is found
in the only extant sermon of the pious Bishop Rowley, a characteristic
passage from which is here given:

        "Now righteousness consisteth not merely in a holy state of
    mind, nor yet in performance of religious rites and obedience to
    the letter of the law.  It is not enough that one be pious and
    just:  one must see to it that others also are in the same state;
    and to this end compulsion is a proper means.  Forasmuch as my
    injustice may work ill to another, so by his injustice may evil be
    wrought upon still another, the which it is as manifestly my duty
    to estop as to forestall mine own tort.  Wherefore if I would be
    righteous I am bound to restrain my neighbor, by force if needful,
    in all those injurious enterprises from which, through a better
    disposition and by the help of Heaven, I do myself restrain."