The Collaborative International Dictionary of English v.0.48:

Tax \Tax\ (t[a^]ks), v. t. [imp. & p. p. Taxed; p. pr. & vb.
   n. Taxing.] [Cf. F. taxer. See Tax, n.]
   1. To subject to the payment of a tax or taxes; to impose a
      tax upon; to lay a burden upon; especially, to exact money
      from for the support of government.
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            We are more heavily taxed by our idleness, pride,
            and folly than we are taxed by government.
                                                  --Franklin.
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   2. (Law) To assess, fix, or determine judicially, the amount
      of; as, to tax the cost of an action in court.
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   3. To charge; to accuse; also, to censure; -- often followed
      by with, rarely by of before an indirect object; as, to
      tax a man with pride.
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            I tax you, you elements, with unkindness. --Shak.
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            Men's virtues I have commended as freely as I have
            taxed their crimes.                   --Dryden.
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            Fear not now that men should tax thine honor. --M.
                                                  Arnold.
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The Collaborative International Dictionary of English v.0.48:

Tax \Tax\, n. [F. taxe, fr. taxer to tax, L. taxare to touch,
   sharply, to feel, handle, to censure, value, estimate, fr.
   tangere, tactum, to touch. See Tangent, and cf. Task,
   Taste.]
   1. A charge, especially a pecuniary burden which is imposed
      by authority. Specifically:
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      (a) A charge or burden laid upon persons or property for
          the support of a government.
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                A farmer of taxes is, of all creditors,
                proverbially the most rapacious.  --Macaulay.
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      (b) Especially, the sum laid upon specific things, as upon
          polls, lands, houses, income, etc.; as, a land tax; a
          window tax; a tax on carriages, and the like.

   Note: Taxes are annual or perpetual, direct or
         indirect, etc.
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      (c) A sum imposed or levied upon the members of a society
          to defray its expenses.
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   2. A task exacted from one who is under control; a
      contribution or service, the rendering of which is imposed
      upon a subject.
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   3. A disagreeable or burdensome duty or charge; as, a heavy
      tax on time or health.
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   4. Charge; censure. [Obs.] --Clarendon.
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   5. A lesson to be learned; a task. [Obs.] --Johnson.
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   Tax cart, a spring cart subject to a low tax. [Eng.]
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   Syn: Impost; tribute; contribution; duty; toll; rate;
        assessment; exaction; custom; demand.
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WordNet (r) 3.0 (2006):

tax
    n 1: charge against a citizen's person or property or activity
         for the support of government [syn: tax, taxation,
         revenue enhancement]
    v 1: levy a tax on; "The State taxes alcohol heavily"; "Clothing
         is not taxed in our state"
    2: set or determine the amount of (a payment such as a fine)
       [syn: tax, assess]
    3: use to the limit; "you are taxing my patience" [syn: tax,
       task]
    4: make a charge against or accuse; "They taxed him failure to
       appear in court"

Moby Thesaurus II by Grady Ward, 1.0:

196 Moby Thesaurus words for "tax":
   accuse, allege, arraign, article, ask, assess, assessment,
   bear hard upon, blackmail, boodle, book, bring accusation,
   bring charges, bring to book, burden, burden with, burthen, busy,
   call, call for, cargo, cess, charge, charge for, cite, claim,
   complain, conscience money, contribution, cumber, customs, demand,
   demand for, denounce, denunciate, direct tax, draft, drain, drive,
   dues, duty, encumber, encumbrance, enjoin, exact, exaction, excise,
   exhaust, extortion, extortionate demand, fag, fasten on,
   fasten upon, finger, freight, freight with, giveaway,
   graduated taxation, hamper, handicap, hang something on, haul,
   heave, heavy demand, impeach, imply, impose, impose on,
   impose upon, imposition, impost, impute, indent, indict,
   indirect tax, inflict on, inflict upon, inform against, inform on,
   insinuate, insistent demand, joint return, keep busy, lade, lay,
   lay charges, lay on, levy, load, lodge a complaint, lodge a plaint,
   make dutiable, nonnegotiable demand, notice, onus, oppress, order,
   overburden, overcarrying, overdoing, overdrive, overemphasis,
   overexercise, overexert, overexertion, overexpenditure, overextend,
   overimportance, overload, overreaching, overreaction, overstrain,
   overtask, overtax, overtaxing, overuse, overweight, overwork,
   pin on, place, pork, prefer charges, press, press charges,
   press hard upon, pressure, pro rata, progressive tax, prorate,
   pull, put, put down, put on, put on report, put upon, rack, rates,
   report, reproach, require, requirement, requisition,
   rest hard upon, rush, rush order, saddle, saddle with, scot,
   separate returns, set, single tax, stick for, strain,
   strain every nerve, stress, stretch, subject to, supererogation,
   supertax, surtax, sweat, sweat blood, take to task, tariff, task,
   taunt with, tax base, tax dodging, tax evasion, tax exemption,
   tax return, tax structure, tax withholding, tax-exempt status,
   taxable income, taxation, taxing, tense, tithe, toll, tribute, try,
   tug, twit, ultimatum, warning, weigh, weigh down, weigh heavy on,
   weigh on, weigh upon, weight, weight down with, withholding tax,
   work, yoke with