The Collaborative International Dictionary of English v.0.48:

Assessment \As*sess"ment\, n. [LL. assessamentum.]
   1. The act of assessing; the act of determining an amount to
      be paid; as, an assessment of damages, or of taxes; an
      assessment of the members of a club.
      [1913 Webster]

   2. A valuation of property or profits of business, for the
      purpose of taxation; such valuation and an adjudging of
      the proper sum to be levied on the property; as, an
      assessment of property or an assessment on property.
      [1913 Webster]

   Note: An assessment is a valuation made by authorized persons
         according to their discretion, as opposed to a sum
         certain or determined by law. It is a valuation of the
         property of those who are to pay the tax, for the
         purpose of fixing the proportion which each man shall
         pay. --Blackstone. Burrill.
         [1913 Webster]

   3. The specific sum levied or assessed.
      [1913 Webster]

   4. An apportionment of a subscription for stock into
      successive installments; also, one of these installments
      (in England termed a "call"). [U. S.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

assessment
    n 1: the classification of someone or something with respect to
         its worth [syn: appraisal, assessment]
    2: an amount determined as payable; "the assessment for repairs
       outraged the club's membership"
    3: the market value set on assets
    4: the act of judging or assessing a person or situation or
       event; "they criticized my judgment of the contestants" [syn:
       judgment, judgement, assessment]

Moby Thesaurus II by Grady Ward, 1.0:

105 Moby Thesaurus words for "assessment":
   Irish dividend, account, allowance, analyzing, appraisal,
   appraisement, appraising, appreciation, apprizal, approximation,
   assessing, assize, assizement, bill, blackmail, blood money,
   calculation, categorization, cess, classification, computation,
   conscience money, contribution, correction, determination,
   direct tax, dual pricing, duty, emolument, estimate, estimation,
   evaluating, evaluation, evaluative criticism, factoring, fee,
   footing, gauging, graduated taxation, grouping, hush money,
   identification, imposition, impost, indirect tax, initiation fee,
   instrumentation, joint return, judgment, levy, measure,
   measurement, measuring, mensuration, metric system, mileage,
   opinion, price determination, pricing, progressive tax,
   quantification, quantization, ranking, rating, reckoning, retainer,
   retaining fee, scot, separate returns, sifting, sifting out,
   single tax, sorting, sorting out, stipend, stock, supertax, surtax,
   survey, surveying, tariff, tax, tax base, tax dodging, tax evasion,
   tax exemption, tax return, tax structure, tax withholding,
   tax-exempt status, taxable income, taxation, telemetering,
   telemetry, tithe, toll, triangulation, tribute, unit pricing,
   valuation, valuing, view, weighing, winnowing, withholding tax



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

ASSESSMENT. The making out a list of property, and fixing its valuation or
appraisement; it is also applied to making out a list of persons, and
appraising their several occupations, chiefly with a view of taxing the said
persons and their property.