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.
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   2. The result of computation; the amount computed.
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   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]