The Collaborative International Dictionary of English v.0.48:

Notation \No*ta"tion\, n. [L. notatio a marking, observing,
   etymology, fr. notare to mark, nota a mark: cf. F. notation.
   See 5th Note.]
   1. The act or practice of recording anything by marks,
      figures, or characters.
      [1913 Webster]

   2. Any particular system of characters, symbols, or
      abbreviated expressions used in art or science, to express
      briefly technical facts, quantities, etc. Esp., the system
      of figures, letters, and signs used in arithmetic and
      algebra to express number, quantity, or operations.
      [1913 Webster]

   3. Literal or etymological signification. [Obs.]
      [1913 Webster]

            "Conscience" is a Latin word, and, according to the
            very notation of it, imports a double or joint
            knowledge.                            --South.
      [1913 Webster]

WordNet (r) 3.0 (2006):

notation
    n 1: a technical system of symbols used to represent special
         things [syn: notation, notational system]
    2: a comment or instruction (usually added); "his notes were
       appended at the end of the article"; "he added a short
       notation to the address on the envelope" [syn: note,
       annotation, notation]
    3: the activity of representing something by a special system of
       marks or characters

Moby Thesaurus II by Grady Ward, 1.0:

173 Moby Thesaurus words for "notation":
   abstract, accent, accent mark, addition, adversaria, aide-memoire,
   alphabet, annotation, apparatus criticus, approximation,
   arrangement, art, bar, binary digit, bit, blueprint, cancel,
   character, charactering, characterization, characters, chart, chit,
   choreography, cipher, code, comment, commentary, commentation,
   conventional representation, copy, credit, custos, dance notation,
   debit, delineation, demonstration, depiction, depictment, diagram,
   differentiation, digit, direct, division, docket, dot,
   double entry, draft, drama, drawing, edition, entry, equation,
   evolution, exegesis, exemplification, expression mark,
   extrapolation, fermata, figuration, figure, footnote, gloss,
   hieroglyphic, hold, hymnal, hymnbook, iconography, ideogram,
   illustration, imagery, imaging, instrumental score, integration,
   interpolation, inversion, involution, item, jotting, key signature,
   lead, letter, libretto, ligature, limning, logogram, logograph,
   lute tablature, map, marginal note, marginalia, mark, measure,
   memo, memoir, memorandum, memorial, metronomic mark, minute,
   minutes, multiplication, music, music paper, music roll,
   musical notation, musical score, note, note of explanation, number,
   numeral, numero, opera, opera score, orchestral score, part, pause,
   piano score, pictogram, picturization, plan, portraiture,
   portrayal, practice, prefigurement, presa, presentment, printing,
   projection, proportion, realization, record, reduction, register,
   registry, reminder, rendering, rendition, representation, schema,
   scholia, scholium, score, script, segno, sheet music, short score,
   sign, signature, signs, single entry, slur, songbook, songster,
   subtraction, swell, syllabary, symbol, symbolism, symbols,
   tablature, tempo mark, text, tie, time signature, transcript,
   transcription, transformation, version, vinculum, vocal score,
   word of explanation, writing, written music