The Collaborative International Dictionary of English v.0.48:

Equity \Eq"ui*ty\, n.; pl. Equities. [F. ['e]quit['e], L.
   aequitas, fr. aequus even, equal. See Equal.]
   1. Equality of rights; natural justice or right; the giving,
      or desiring to give, to each man his due, according to
      reason, and the law of God to man; fairness in
      determination of conflicting claims; impartiality.
      [1913 Webster]

            Christianity secures both the private interests of
            men and the public peace, enforcing all justice and
            equity.                               --Tillotson.
      [1913 Webster]

   2. (Law) An equitable claim; an equity of redemption; as, an
      equity to a settlement, or wife's equity, etc.
      [1913 Webster]

            I consider the wife's equity to be too well settled
            to be shaken.                         --Kent.
      [1913 Webster]

   3. (Law) A system of jurisprudence, supplemental to law,
      properly so called, and complemental of it.
      [1913 Webster]

            Equity had been gradually shaping itself into a
            refined science which no human faculties could
            master without long and intense application.
                                                  --Macaulay.
      [1913 Webster]

   Note: Equitable jurisprudence in England and in the United
         States grew up from the inadequacy of common-law forms
         to secure justice in all cases; and this led to
         distinct courts by which equity was applied in the way
         of injunctions, bills of discovery, bills for specified
         performance, and other processes by which the merits of
         a case could be reached more summarily or more
         effectively than by common-law suits. By the recent
         English Judicature Act (1873), however, the English
         judges are bound to give effect, in common-law suits,
         to all equitable rights and remedies; and when the
         rules of equity and of common law, in any particular
         case, conflict, the rules of equity are to prevail. In
         many jurisdictions in the United States, equity and
         common law are thus blended; in others distinct equity
         tribunals are still maintained. See Chancery.
         [1913 Webster]

   Equity of redemption (Law), the advantage, allowed to a
      mortgageor, of a certain or reasonable time to redeem
      lands mortgaged, after they have been forfeited at law by
      the nonpayment of the sum of money due on the mortgage at
      the appointed time. --Blackstone.

   Syn: Right; justice; impartiality; rectitude; fairness;
        honesty; uprightness. See Justice.
        [1913 Webster]

WordNet (r) 3.0 (2006):

equity
    n 1: the difference between the market value of a property and
         the claims held against it
    2: the ownership interest of shareholders in a corporation
    3: conformity with rules or standards; "the judge recognized the
       fairness of my claim" [syn: fairness, equity] [ant:
       inequity, unfairness]

Moby Thesaurus II by Grady Ward, 1.0:

205 Moby Thesaurus words for "equity":
   Code Napoleon, Corpus Juris Canonici, Napoleonic code, Roman law,
   absolute interest, admiralty law, assessable stock,
   authorized capital stock, balance, benefit, blue chip,
   blue chip stock, blue law, body of law, borrowed stock, canon law,
   capital stock, capitulary, case law, chancery law, civil law,
   claim, code, code of laws, codification, coequality, coextension,
   commercial law, common, common law, common stock, compatibility,
   constitutional law, contingent interest,
   convertible preferred stock, corporate stock, corporation law,
   corpus juris, correlation, correspondence, criminal law, crown law,
   cumulative preferred stock, cyclical stock, decree law,
   defensibility, defensive stock, deferred stock, digest,
   digest of law, disinterest, disinterestedness, droit des gens,
   drumhead justice, dry law, dueness, easement, ecclesiastical law,
   eighth stock, equality, equation, equilibrium, equipoise,
   equipollence, equiponderance, equitable interest, equitableness,
   equities, equity security, equivalence, equivalency, estate,
   evenhandedness, evenness, exchangeability, fair play,
   fair-mindedness, fairness, fancies, floating stock, gag law,
   give-and-take, glamour issue, growth stock, guaranteed stock,
   high-flier, high-mindedness, holding, hot issue,
   hypothecated stock, identity, impartiality, inactive stock,
   income stock, interchangeability, interest, international law,
   issued capital stock, judiciousness, jus civile, jus commune,
   jus inter gentes, jus publicum, justice, justifiability,
   justifiableness, justification, justness, law merchant, lawfulness,
   legality, letter stock, levelness, lex domicilii, lex fori,
   lex loci, lex mercatorum, lex non scripta, lex scripta, lex situs,
   likeness, limitation, loaned stock, local law, long stock,
   martial law, measure for measure, meetness, nemesis, neutrality,
   nonassessable stock, nonvoting stock, objectivity, open-mindedness,
   ordinary shares, pale blue chip, pandect, par, parallelism, parity,
   part, participating preferred stock, penal code, penal law,
   penny stock, percentage, poetic justice, poise, positive law,
   preference stock, preferred stock, properness, proportion,
   propriety, protective stock, public law, quarter stock, rails,
   retributive justice, reverse split, right, right of entry,
   rightfulness, rightness, rude justice, sameness, scales of justice,
   sea law, seasoned stock, settlement, share ledger, shares,
   short stock, special situation stock, specialty stock,
   speculative stock, split, stake, standard stock, statute law,
   steels, stock, stock ledger, stock list, stock split, stocks,
   strict settlement, substantive law, summary justice, symmetry,
   ten-share unit stock, title, tolerance, treasury stock, trust,
   unissued capital stock, unwritten law, use, utilities,
   vested interest, voting stock, warrantability, warrantedness,
   what is right, written law



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

EQUITY. In the early history of the law, the sense affixed to this word was
exceedingly vague and uncertain. This was owing, in part, to the fact, that
the chancellors of those days were either statesmen or ecclesiastics,
perhaps not very scrupulous in the exercise of power. It was then asserted
that equity was bounded by no certain limits or rules, and that it was alone
controlled by conscience and natural justice. 3 Bl. Com. 43-3, 440, 441.
     2. In a moral sense, that is called equity which is founded, ex oequo
et bono, in natural justice, in honesty, and in right. In an enlarged. legal
view, "equity, in its true and genuine meaning, is the soul and spirit of
the law; positive law is construed, and rational law is made by it. In this,
equity is made synonymous with justice; in that, to the true and sound
interpretation of the rule." 3 Bl. Com. 429. This equity is justly said to
be a supplement to the laws; but it must be directed by science. The Roman
law will furnish him with sure guides, and safe rules. In that code will be
found, fully developed, the first principles and the most important
consequences of natural right. "From the moment when principles of decision
came to be acted upon in chancery," says Mr. Justice Story, "the Roman law
furnished abundant materials to erect a superstructure, at once solid,
convenient and lofty, adapted to human wants, and enriched by the aid of
human wisdom, experience and learning." Com. on Eq. Jur. Sec. 23 Digest, 54.
     3. But equity has a more restrained and qualified meaning. The remedies
for the redress of wrongs, and for the enforcement of rights, are
distinguished into two classes, first, those which are administered in
courts of common law; and, secondly, those which are administered in courts
of equity. Rights which are recognized and protected, and wrongs which are
redressed by the former courts, are called legal rights and legal injuries.
Rights which are recognized and protected, and wrongs which are redressed by
the latter courts only, are called equitable rights and equitable injuries
The former are said to be rights and wrongs at common law, and the remedies,
therefore, are remedies at common law; the latter are said to be rights and
wrongs in equity, and the remedies, therefore, are remedies in equity.
Equity jurisprudence may, therefore, properly be said to be that portion of
remedial justice which is exclusively administered by a court of equity, as
contradistinguished from that remedial justice, which is exclusively
administered by a court of law. Story, Eq. Sec. 25. Vide Chancery, and the
authorities there cited; and 3 Chit. Bl. Com. 425 n. 1. Dane's Ab. h.t.;
Ayl. Pand. 37; Fonbl. Eq. b. 1, c. 1; Wooddes. Lect. 114 Bouv. Inst. Index,
h.t.



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

EQUITY, COURT OF. A court of equity is one which administers justice, where
there are no legal rights, or legal rights, but courts of law do not afford
a complete, remedy, and where the complainant has also an equitable right.
Vide Chancery.