The Collaborative International Dictionary of English v.0.48:

Substance \Sub"stance\, n. [F., fr. L. substantia, fr. substare
   to be under or present, to stand firm; sub under + stare to
   stand. See Stand.]
   1. That which underlies all outward manifestations;
      substratum; the permanent subject or cause of phenomena,
      whether material or spiritual; that in which properties
      inhere; that which is real, in distinction from that which
      is apparent; the abiding part of any existence, in
      distinction from any accident; that which constitutes
      anything what it is; real or existing essence.
      [1913 Webster]

            These cooks, how they stamp, and strain, and grind,
            And turn substance into accident!     --Chaucer.
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            Heroic virtue did his actions guide,
            And he the substance, not the appearance, chose.
                                                  --Dryden.
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   2. The most important element in any existence; the
      characteristic and essential components of anything; the
      main part; essential import; purport.
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            This edition is the same in substance with the
            Latin.                                --Bp. Burnet.
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            It is insolent in words, in manner; but in substance
            it is not only insulting, but alarming. --Burke.
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   3. Body; matter; material of which a thing is made; hence,
      substantiality; solidity; firmness; as, the substance of
      which a garment is made; some textile fabrics have little
      substance.
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   4. Material possessions; estate; property; resources.
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            And there wasted his substance with riotous living.
                                                  --Luke xv. 13.
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            Thy substance, valued at the highest rate,
            Can not amount unto a hundred marks.  --Shak.
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            We are destroying many thousand lives, and
            exhausting our substance, but not for our own
            interest.                             --Swift.
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   5. (Theol.) Same as Hypostasis, 2.
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The Collaborative International Dictionary of English v.0.48:

Substance \Sub"stance\, v. t.
   To furnish or endow with substance; to supply property to; to
   make rich. [Obs.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

substance
    n 1: the real physical matter of which a person or thing
         consists; "DNA is the substance of our genes"
    2: the choicest or most essential or most vital part of some
       idea or experience; "the gist of the prosecutor's argument";
       "the heart and soul of the Republican Party"; "the nub of the
       story" [syn: kernel, substance, core, center,
       centre, essence, gist, heart, heart and soul,
       inwardness, marrow, meat, nub, pith, sum, nitty-
       gritty]
    3: the idea that is intended; "What is the meaning of this
       proverb?" [syn: meaning, substance]
    4: material of a particular kind or constitution; "the immune
       response recognizes invading substances"
    5: considerable capital (wealth or income); "he is a man of
       means" [syn: means, substance]
    6: what a communication that is about something is about [syn:
       message, content, subject matter, substance]
    7: a particular kind or species of matter with uniform
       properties; "shigella is one of the most toxic substances
       known to man"

Moby Thesaurus II by Grady Ward, 1.0:

308 Moby Thesaurus words for "substance":
   Swiss bank account, actuality, affective meaning, affluence, air,
   amount, amplitude, assets, atom, atomic particles, atoms, axiom,
   balance, bank account, basis, bearing, being, bench mark,
   best part, better part, body, bottom, bottom dollar,
   bottomless purse, brute matter, budget, building block,
   bulging purse, bulk, burden, call, cardinal point, case,
   cash reserves, cause, center, chapter, checking account,
   chemical element, chief thing, climax, coloring, command of money,
   component, composition, concern, concreteness, connotation,
   consequence, constituent, core, cornerstone, corporeality, corpus,
   crisis, critical point, crux, denotation, density, distillate,
   distillation, drift, durability, earth, easy circumstances, effect,
   element, elementary particle, elementary unit, elixir,
   embarras de richesses, entity, essence, essential,
   essential matter, essentiality, exchequer, extension, extent,
   fabric, finances, fire, firmness, flower, focus,
   focus of attention, focus of interest, force, fortune, foundation,
   fund, fundamental, fundamental particle, funds, generality, gist,
   gold, good reason, grammatical meaning, gravamen, great point,
   ground, grounds, handsome fortune, head, heading, heart,
   high income, high point, high tax bracket, hyle, hypostasis, idea,
   impact, implication, import, important thing, independence,
   individual, inner essence, intension, issue, kernel, keystone,
   kitty, landmark, lexical meaning, life savings, literal meaning,
   living issue, lucre, luxuriousness, magnitude, main body,
   main point, main thing, major part, majority, mammon, marrow, mass,
   material, material basis, material point, material resources,
   material wealth, material world, materiality, materials, materiel,
   matter, matter in hand, meaning, meaningfulness, means, measure,
   measurement, meat, medium, milestone, molecule, monad, money,
   money to burn, moneybags, moneys, most, motif, motive,
   natural world, nature, nest egg, nub, nubbin, nucleus, numbers,
   nuts and bolts, object, opulence, opulency, overtone, palpability,
   pecuniary resources, pelf, pertinence, physical world, pith, pivot,
   plenum, plurality, pocket, point, point at issue,
   point in question, ponderability, pool, possessions, postulate,
   practical consequence, principle, problem, property, prosperity,
   prosperousness, purport, purse, quantity, quantum, question, quid,
   quiddity, quintessence, quintessential, range of meaning,
   raw material, real issue, real meaning, reality, reason, recap,
   recapitulation, reference, referent, relation, relevance, reserves,
   resources, resume, riches, richness, right, rubric, run-through,
   rundown, salient point, sap, savings, savings account, scope,
   semantic cluster, semantic field, sense, short, significance,
   signification, significatum, signifie, sine qua non, solidity,
   soul, soundness, span of meaning, spirit, stability, staple,
   steadiness, stock, store, stoutness, strength, structural meaning,
   stuff, sturdiness, subject, subject matter, subject of thought,
   substances, substantiality, substantialness, substantive point,
   substratum, sum, sum and substance, sum total, summary, summation,
   supply, symbolic meaning, tangibility, tangible, tenor, text,
   the bottom line, the four elements, the nitty-gritty, the point,
   theme, thrust, topic, totality of associations, toughness,
   transferred meaning, treasure, turning point, unadorned meaning,
   undertone, unit of being, unregistered bank account, upper bracket,
   upshot, value, warrant, water, wealth, wealthiness, wherewithal,
   whole, worth



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

SUBSTANCE, evidence. That which is essential; it is used in opposition to
form.
     2. It is a general rule, that on any issue it is sufficient to prove
the substance of the issue. For example, in a case where the defendant
pleaded payment of the principal sum and all interest due, and it appeared
in evidence that a gross sum was paid, not amounting to the full interest,
but accepted by the plaintiff as full payment, the proof was held to be
sufficient. 2 Str. 690; 1 Phil. Ev. 161.