The Collaborative International Dictionary of English v.0.48:

Computation \Com`pu*ta"tion\, n. [L. computatio: cf. F.
   computation.]
   1. The act or process of computing; calculation; reckoning.
      [1913 Webster]

            By just computation of the time.      --Shak.
      [1913 Webster]

            By a computation backward from ourselves. --Bacon.
      [1913 Webster]

   2. The result of computation; the amount computed.
      [1913 Webster]

   3. (Computers) The process of performing arithmetical or
      logical operations, on data by an electronic device.
      [PJC]

   Syn: Reckoning; calculation; estimate; account.
        [1913 Webster]

WordNet (r) 3.0 (2006):

computation
    n 1: the procedure of calculating; determining something by
         mathematical or logical methods [syn: calculation,
         computation, computing]
    2: problem solving that involves numbers or quantities [syn:
       calculation, computation, figuring, reckoning]

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "computation":
   accounting, adding, adding machine, analysis, appraisal,
   appraisement, approximation, arithmetic, assessment, assize,
   assizement, automatic electronic navigation, braking, calculation,
   calculator, calculus, casting, ciphering, coordination, correction,
   determination, estimate, estimation, evaluation, fact distribution,
   figuring, footing, forecasts, gauging, inspection, instrumentation,
   manipulation, measure, measurement, measuring, mensuration,
   metric system, nonlinear calibrations, output measurement,
   processing, quantification, quantization, rating, reckoning,
   record keeping, steering, supersonic flow detection, survey,
   surveying, telemetering, telemetry, totaling, toting,
   triangulation, valuation



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

COMPUTATION counting, calculation. It is a reckoning or ascertaining the
number of any thing.
     2. It is sometimes used in the common law for the true reckoning or
account of time. Time is computed in two ways; first, naturally, counting
years, days and hours; and secondly, civilly, that is, that when the last
part of the time has once commenced, it is considered as accomplished.
Savig. Dr. Rom. Sec. 182. See Infant; Fraction. For the computation of a
year, see Com. Dig. Ann; of a mouth, Com. Dig. Temps. A; 1 John. Cas. 100 15
John. R. 120; 2 Mass. 170, n.; 4 Mass. 460; 4 Dall. 144; 3 S. & R. 169; of a
day, vide Day.; and 3, Burr 1434; 11 Mass. 204; 2 Browne, 18; Dig. 3, 4, 5;
Salk. 625; 3 Wils. 274.
     3. It is a general rule that when an act is to be done within a certain
time, one day is to be taken inclusively, and one exclusively. Vide Lofft,
276; Dougl. 463; 2 Chit. Pr. 69; 3 Id. 108, 9; 3 T. R. 623; 2 Campb. R. 294;
4 Man. and Ryl. 300, n. (b) 5 Bingh. R. 339; S. C. 15, E. C. L. R. 462; 3
East, R. 407; Hob. 139; 4 Moore, R. 465; Har. Dig. Time, computation of; 3
T. R. 623; 5 T. R. 283; 2 Marsh. R. 41; 22 E. C. L. R. 270; 13, E, C. L. R.
238; 24 E. C. L. R. 53; 4 Wasb. C. C. R. 232; 1 Ma-son, 176; 1 Pet. 60; 4
Pet. 349; 9 Cranch, 104; 9 Wheat. 581. Vide Day; Hour; Month; Year.