The Collaborative International Dictionary of English v.0.48:

Estimate \Es"ti*mate\, n.
   A valuing or rating by the mind, without actually measuring,
   weighing, or the like; rough or approximate calculation; as,
   an estimate of the cost of a building, or of the quantity of
   water in a pond.
   [1913 Webster]

         Weigh success in a moral balance, and our whole
         estimate is changed.                     --J. C.
                                                  Shairp.

   Syn: Estimate, Estimation, Esteem.

   Usage: The noun estimate, like its verb, supposes chiefly an
          exercise of judgment in determining the amount,
          importance, or magnitude of things, with their other
          exterior relations; as, an estimate of expenses
          incurred; a true estimate of life, etc. Esteem is a
          moral sentiment made up of respect and attachment, --
          the valuation of a person as possessing useful
          qualities or real worth. Thus we speak of the esteem
          of the wise and good as a thing greatly to be desired.
          Estimation seems to waver between the two. In our
          version of the Scriptures it is used simply for
          estimate; as, "If he be poorer than thy estimation."
          --Lev. xxvii. 8. In other cases, it verges toward
          esteem; as, "I know him to be of worth and worthy
          estimation." --Shak. It will probably settle down at
          last on this latter sense. "Esteem is the value we
          place upon some degree of worth. It is higher than
          simple approbation, which is a decision of judgment.
          It is the commencement of affection." --Gogan.
          [1913 Webster]

                No; dear as freedom is, and in my heart's
                Just estimation prized above all price.
                                                  --Cowper.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Estimate \Es"ti*mate\, v. t. [imp. & p. p. Estimated; p. pr. &
   vb. n. Estimating.] [L. aestimatus, p. p. of aestimare. See
   Esteem, v. t.]
   1. To judge and form an opinion of the value of, from
      imperfect data, -- either the extrinsic (money), or
      intrinsic (moral), value; to fix the worth of roughly or
      in a general way; as, to estimate the value of goods or
      land; to estimate the worth or talents of a person.
      [1913 Webster]

            It is by the weight of silver, and not the name of
            the piece, that men estimate commodities and
            exchange them.                        --Locke.
      [1913 Webster]

            It is always very difficult to estimate the age in
            which you are living.                 --J. C.
                                                  Shairp.
      [1913 Webster]

   2. To from an opinion of, as to amount,, number, etc., from
      imperfect data, comparison, or experience; to make an
      estimate of; to calculate roughly; to rate; as, to
      estimate the cost of a trip, the number of feet in a piece
      of land.

   Syn: To appreciate; value; appraise; prize; rate; esteem;
        count; calculate; number. -- To Estimate, Esteem.
        Both these words imply an exercise of the judgment.
        Estimate has reference especially to the external
        relations of things, such as amount, magnitude,
        importance, etc. It usually involves computation or
        calculation; as, to estimate the loss or gain of an
        enterprise. Esteem has reference to the intrinsic or
        moral worth of a person or thing. Thus, we esteem a man
        for his kindness, or his uniform integrity. In this
        sense it implies a mingled sentiment of respect and
        attachment. We esteem it an honor to live in a free
        country. See Appreciate.
        [1913 Webster]

WordNet (r) 3.0 (2006):

estimate
    n 1: an approximate calculation of quantity or degree or worth;
         "an estimate of what it would cost"; "a rough idea how long
         it would take" [syn: estimate, estimation,
         approximation, idea]
    2: a judgment of the qualities of something or somebody; "many
       factors are involved in any estimate of human life"; "in my
       estimation the boy is innocent" [syn: estimate,
       estimation]
    3: a document appraising the value of something (as for
       insurance or taxation) [syn: appraisal, estimate,
       estimation]
    4: a statement indicating the likely cost of some job; "he got
       an estimate from the car repair shop"
    5: the respect with which a person is held; "they had a high
       estimation of his ability" [syn: estimate, estimation]
    v 1: judge tentatively or form an estimate of (quantities or
         time); "I estimate this chicken to weigh three pounds"
         [syn: estimate, gauge, approximate, guess, judge]
    2: judge to be probable [syn: calculate, estimate, reckon,
       count on, figure, forecast]

Moby Thesaurus II by Grady Ward, 1.0:

201 Moby Thesaurus words for "estimate":
   account as, add, adjudge, adjudicate, algebraize, analyzing,
   appraisal, appraise, appraisement, appraising, appreciate,
   appreciation, approximate, approximation, ascertain, assay, assess,
   assessing, assessment, assize, assizement, assume, assumption,
   attitude, be afraid, belief, believe, calculate, calculation,
   calibrate, caliper, call, cast, check a parameter, cipher, class,
   climate of opinion, common belief, community sentiment,
   computation, compute, conceit, conceive, concept, conception,
   conclusion, conjecture, consensus gentium, consider, consideration,
   correction, count, daresay, decide, deduce, deem, determination,
   determine, dial, discover, divide, dope out, enumerate, esteem,
   estimation, ethos, evaluate, evaluating, evaluation,
   evaluative criticism, expect, extract roots, eye, fancy, fathom,
   feeling, figure, figure in, figure out, form an estimate, gauge,
   gauging, general belief, give an appreciation, graduate, guess,
   guesstimate, have a hunch, have an idea, have an impression,
   have an inkling, have the idea, hold, hold as, idea, imagine,
   impression, infer, instrumentation, judge, judgement, judgment,
   lights, look upon as, maintain, make an estimation, mark, measure,
   measurement, measuring, mensurate, mensuration, mete, meter,
   metric system, mind, multiply, mystique, notion, observation,
   opine, opinion, pace, personal judgment, place, plumb,
   point of view, popular belief, position, posture, presume,
   presumption, prevailing belief, price, prize, probe, projection,
   public belief, public opinion, put, quantification, quantify,
   quantization, quantize, rank, ranking, rate, rating, reaction,
   reckon, reckoning, regard, round, score, sense, sentiment, set at,
   set down as, settle, sight, size, size up, sound, span, stance,
   step, stock, subtract, sum, suppose, surmise, survey, surveying,
   suspect, take, take a reading, take account of, take for, take it,
   tally, telemetering, telemetry, theory, think, thinking, thought,
   triangulate, triangulation, trow, valuate, valuation, value,
   valuing, view, view as, viewpoint, way of thinking, ween, weigh,
   weighing, work out