The Collaborative International Dictionary of English v.0.48:

Actuary \Ac"tu*a*ry\, n.; pl. Actuaries. [L. actuarius
   copyist, clerk, fr. actus, p. p. of agere to do, act.]
   1. (Law) A registrar or clerk; -- used originally in courts
      of civil law jurisdiction, but in Europe used for a clerk
      or registrar generally.
      [1913 Webster]

   2. The computing official of an insurance company; one whose
      profession it is to calculate for insurance companies the
      risks and premiums for life, fire, and other insurances.
      [1913 Webster]

WordNet (r) 3.0 (2006):

actuary
    n 1: someone versed in the collection and interpretation of
         numerical data (especially someone who uses statistics to
         calculate insurance premiums) [syn: statistician,
         actuary]

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "actuary":
   CA, CPA, abacist, accident insurance, accountant,
   accountant general, annuity, assurance, auditor,
   aviation insurance, bail bond, bank accountant, bank examiner,
   bond, bookkeeper, business life insurance, calculator,
   casualty insurance, certificate of insurance,
   certified public accountant, chartered accountant, clerk,
   comptroller, computer, controller, cost accountant, cost keeper,
   court bond, credit insurance, credit life insurance, deductible,
   endowment insurance, estimator, family maintenance policy,
   fidelity bond, fidelity insurance, figurer, flood insurance,
   fraternal insurance, government insurance, health insurance,
   industrial life insurance, insurance, insurance agent,
   insurance broker, insurance company, insurance man,
   insurance policy, interinsurance, journalizer, liability insurance,
   license bond, limited payment insurance, major medical insurance,
   malpractice insurance, marine insurance, mutual company,
   ocean marine insurance, permit bond, policy, reckoner, recorder,
   registrar, robbery insurance, social security, statistician,
   stock company, term insurance, theft insurance, underwriter



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

ACTUARY. A clerk in some corporations vested with various powers. In the
ecclesiastical law he is a clerk who registers the acts and constitutions of
the convocation.