The Collaborative International Dictionary of English v.0.48:

Deduct \De*duct"\, v. t. [imp. & p. p. Deducted; p. pr. & vb.
   n. Deducting.] [L. deductus, p. p. of deducere to deduct.
   See Deduce.]
   1. To lead forth or out. [Obs.]
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            A people deducted out of the city of Philippos.
                                                  --Udall.
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   2. To take away, separate, or remove, in numbering,
      estimating, or calculating; to subtract; -- often with
      from or out of.
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            Deduct what is but vanity, or dress.  --Pope.
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            Two and a half per cent should be deducted out of
            the pay of the foreign troops.        --Bp. Burnet.
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            We deduct from the computation of our years that
            part of our time which is spent in . . . infancy.
      --Norris.
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   3. To reduce; to diminish. [Obs.] "Do not deduct it to days."
      --Massinger.
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WordNet (r) 3.0 (2006):

deduct
    v 1: make a subtraction; "subtract this amount from my paycheck"
         [syn: subtract, deduct, take off] [ant: add, add
         together]
    2: retain and refrain from disbursing; of payments; "My employer
       is withholding taxes" [syn: withhold, deduct, recoup]
    3: reason by deduction; establish by deduction [syn: deduce,
       infer, deduct, derive]

Moby Thesaurus II by Grady Ward, 1.0:

75 Moby Thesaurus words for "deduct":
   abate, abrade, abridge, abstract, allow, bate, charge off, collect,
   compress, conclude, curtail, cut, cut back, cut down, damp, dampen,
   decrease, deduce, deflate, depreciate, depress, derive, derogate,
   detract, diminish, discount, disparage, downgrade, drain, draw,
   draw back, eat away, erode, extract, file away, gather, impair,
   judge, kick back, knock off, leach, lessen, lower, make,
   make allowance, make out, pare, purify, rebate, reduce, refine,
   refund, remove, retrench, roll back, rub away, scale down, shorten,
   simplify, step down, subduct, subtract, take, take a premium,
   take away, take from, take off, take out, thin, thin out,
   tune down, wear away, weed, withdraw, write off