The Collaborative International Dictionary of English v.0.48:

Estimation \Es`ti*ma"tion\, n. [L. aestimatio, fr. aestimare:
   cf. F. estimation. See Esteem, v. t.]
   1. The act of estimating. --Shak.
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   2. An opinion or judgment of the worth, extent, or quantity
      of anything, formed without using precise data; valuation;
      as, estimations of distance, magnitude, amount, or moral
      qualities.
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            If he be poorer that thy estimation, then he shall
            present himself before the priest, and the priest,
            and the priest shall value him.       --Lev. xxvii.
                                                  8.
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   3. Favorable opinion; esteem; regard; honor.
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            I shall have estimation among multitude, and honor
            with the elders.                      --Wisdom viii.
                                                  10.
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   4. Supposition; conjecture.
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            I speak not this in estimation,
            As what I think might be, but what I know. --Shak.

   Syn: Estimate; calculation; computation; appraisement;
        esteem; honor; regard. See Estimate, n.
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WordNet (r) 3.0 (2006):

estimation
    n 1: a document appraising the value of something (as for
         insurance or taxation) [syn: appraisal, estimate,
         estimation]
    2: the respect with which a person is held; "they had a high
       estimation of his ability" [syn: estimate, estimation]
    3: 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]
    4: 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]