The Collaborative International Dictionary of English v.0.48:

Symbol \Sym"bol\ (s[i^]m"b[o^]l), n. [L. symbolus, symbolum, Gr.
   sy`mbolon a sign by which one knows or infers a thing, from
   symba`llein to throw or put together, to compare; sy`n with +
   ba`llein to throw: cf. F. symbole. Cf. Emblem, Parable.]
   1. A visible sign or representation of an idea; anything
      which suggests an idea or quality, or another thing, as by
      resemblance or by convention; an emblem; a representation;
      a type; a figure; as, the lion is the symbol of courage;
      the lamb is the symbol of meekness or patience.
      [1913 Webster]

            A symbol is a sign included in the idea which it
            represents, e. g., an actual part chosen to
            represent the whole, or a lower form or species used
            as the representative of a higher in the same kind.
                                                  --Coleridge.
      [1913 Webster]

   2. (Math.) Any character used to represent a quantity, an
      operation, a relation, or an abbreviation.
      [1913 Webster]

   Note: In crystallography, the symbol of a plane is the
         numerical expression which defines its position
         relatively to the assumed axes.
         [1913 Webster]

   3. (Theol.) An abstract or compendium of faith or doctrine; a
      creed, or a summary of the articles of religion.
      [1913 Webster]

   4. [Gr. ? contributions.] That which is thrown into a common
      fund; hence, an appointed or accustomed duty. [Obs.]
      [1913 Webster]

            They do their work in the days of peace . . . and
            come to pay their symbol in a war or in a plague.
                                                  --Jer. Taylor.
      [1913 Webster]

   5. Share; allotment. [Obs.]
      [1913 Webster]

            The persons who are to be judged . . . shall all
            appear to receive their symbol.       --Jer. Taylor.
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   6. (Chem.) An abbreviation standing for the name of an
      element and consisting of the initial letter of the Latin
      or New Latin name, or sometimes of the initial letter with
      a following one; as, C for carbon, Na for sodium
      (Natrium), Fe for iron (Ferrum), Sn for tin (Stannum),
      Sb for antimony (Stibium), etc. See the list of names
      and symbols under Element.
      [1913 Webster]

   Note: In pure and organic chemistry there are symbols not
         only for the elements, but also for their grouping in
         formulas, radicals, or residues, as evidenced by their
         composition, reactions, synthesis, etc. See the diagram
         of Benzene nucleus, under Benzene.
         [1913 Webster]

   Syn: Emblem; figure; type. See Emblem.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Symbol \Sym"bol\, v. t.
   To symbolize. [R.] --Tennyson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

symbol
    n 1: an arbitrary sign (written or printed) that has acquired a
         conventional significance
    2: something visible that by association or convention
       represents something else that is invisible; "the eagle is a
       symbol of the United States" [syn: symbol, symbolization,
       symbolisation, symbolic representation]

Moby Thesaurus II by Grady Ward, 1.0:

272 Moby Thesaurus words for "symbol":
   abbreviation, accent, accent mark, acronym, agent, allegory,
   alphabet, alphabetic character, alternate, alternative, analogy,
   armory, arms, art, attribute, backup, badge, badge of office,
   badges, banner, bar, baton, bearing, binary digit, bit, blazonry,
   blueprint, brand, brassard, button, cancel, cap and gown, case,
   case in point, chain, chain of office, change, changeling,
   character, charactering, characterization, charactery, chart,
   choreography, cipher, class ring, coat of arms, cockade, code,
   collar, colophon, comparison, conventional representation,
   conventional symbol, copy, counterfeit, crest, cross, cryptogram,
   custos, dance notation, decoration, delineation, demonstration,
   depiction, depictment, deputy, design, device, diagram, digit,
   direct, dot, double, drama, drawing, dress, dummy, eagle, emblem,
   emblems, ensigns, equal, equivalent, ersatz, escutcheon, example,
   exchange, exemplar, exemplification, explanation, exponent,
   expression mark, fake, fasces, father symbol, fermata,
   fertility symbol, figuration, figure, figurehead, fill-in, flag,
   fleur-de-lis, ghost, ghostwriter, glosseme, graph, grapheme,
   hammer and sickle, heraldry, hieroglyphic, hold, icon, iconography,
   iconology, ideogram, illustration, image, imagery, imaging,
   imitation, indication, initialism, insignia, instance,
   key signature, lapel pin, lead, letter, lexeme, lexical form,
   lexigraphic character, ligature, limning, livery, locum tenens,
   logo, logogram, logograph, logotype, love knot, mace, makeshift,
   mantle, map, mark, markings, measure, medal, metaphor, metonymy,
   metronomic mark, monogram, morpheme, mortarboard, mother symbol,
   motif, musical notation, next best thing, notation, note, number,
   numeral, numero, object lesson, old school tie, password, pattern,
   pause, pennant, personnel, phallic symbol, phonetic character,
   phonetic symbol, phony, phrase, pictogram, pictographic character,
   picturization, pin, pinch hitter, plan, portraiture, portrayal,
   prefigurement, presa, presentment, printing, projection, proxy,
   realization, regalia, relevant instance, relief, rendering,
   rendition, replacement, representation, representative, reserves,
   ring, ringer, rose, schema, school ring, score, script,
   second string, secondary, segno, semasiological unit, sememe,
   shamrock, shibboleth, sigillography, sign, signature, signifiant,
   significant, skull and crossbones, slur, spares, sphragistics,
   staff, stamp, stand-in, standard, sub, substituent, substitute,
   substitution, succedaneum, superseder, supplanter, surrogate,
   swastika, swell, syllabary, syllabic, symbolic system, symbolism,
   symbolization, symbology, synecdoche, tablature, tartan,
   tempo mark, term, third string, thistle, tie, time signature,
   token, totem, totem pole, type, typical example, understudy,
   uniform, universal symbol, utility player, verge, vicar,
   vice-president, vice-regent, vinculum, wand, watchword, word,
   writing, written character



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

SYMBOL. A sign; a token; a representation of one thing by another.
     2. A symbolical delivery is equivalent, in many cases, in its legal
effects, to actual delivery; as, for example, the delivery of the keys of a
warehouse in which goods are deposited, is a delivery sufficient to transfer
the property. 1 Atk. 171; 5 John. 335; 2 T. R. 462; 7 T. R. 71; 2 Campb.
243; 1 East, R. 194; 3 Caines, 182; 1 Esp. 598; 3 B. & C. 423.



The Devil's Dictionary (1881-1906):

SYMBOL, n.  Something that is supposed to typify or stand for
something else.  Many symbols are mere "survivals" -- things which
having no longer any utility continue to exist because we have
inherited the tendency to make them; as funereal urns carved on
memorial monuments.  They were once real urns holding the ashes of the
dead.  We cannot stop making them, but we can give them a name that
conceals our helplessness.