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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The Collaborative International Dictionary of English v.0.48:

Annual \An"nu*al\, n.
   1. A thing happening or returning yearly; esp. a literary
      work published once a year.
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   2. Anything, especially a plant, that lasts but one year or
      season; an annual plant.
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            Oaths . . . in some sense almost annuals; . . . and
            I myself can remember about forty different sets.
                                                  --Swift.
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   3. (R. C. Ch.) A Mass for a deceased person or for some
      special object, said daily for a year or on the
      anniversary day.
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The Collaborative International Dictionary of English v.0.48:

Annual \An"nu*al\ (?; 135), a. [OE. annuel, F. annuel, fr. L.
   annualis, fr. annus year. Cf. Annals.]
   1. Of or pertaining to a year; returning every year; coming
      or happening once in the year; yearly.
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            The annual overflowing of the river [Nile]. --Ray.
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   2. Performed or accomplished in a year; reckoned by the year;
      as, the annual motion of the earth.
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            A thousand pound a year, annual support. --Shak.
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   2. Lasting or continuing only one year or one growing season;
      requiring to be renewed every year; as, an annual plant;
      annual tickets. --Bacon.
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WordNet (r) 3.0 (2006):

annual
    adj 1: completing its life cycle within a year; "a border of
           annual flowering plants" [syn: annual, one-year]
           [ant: biennial, perennial, two-year]
    2: occurring or payable every year; "an annual trip to Paris";
       "yearly medical examinations"; "annual (or yearly) income"
       [syn: annual, yearly]
    n 1: (botany) a plant that completes its entire life cycle
         within the space of a year
    2: a reference book that is published regularly once every year
       [syn: annual, yearly, yearbook]

Moby Thesaurus II by Grady Ward, 1.0:

132 Moby Thesaurus words for "annual":
   Domesday Book, account, account book, account rendered, accounting,
   acta, address book, adversaria, album, amphibian, angiosperm,
   appointment calendar, appointment schedule, aquatic plant,
   biannual, biennial, bimonthly, biweekly, blankbook, blotter, brief,
   bulletin, calendar, cashbook, catalog, catamenial, census report,
   centenary, centennial, classified catalog, commonplace book,
   cosmopolite, court calendar, cutting, daily, daybook, decennial,
   deciduous plant, desk calendar, diary, dicot, dicotyledon, diptych,
   diurnal, docket, election returns, engagement book, ephemeral,
   ephemeris, evergreen, exotic, flowering plant, fortnightly, fungus,
   gametophyte, gazette, gymnosperm, hebdomadal, hourly, hydrophyte,
   journal, ledger, log, logbook, loose-leaf notebook, magazine,
   memo book, memorandum book, memory book, menstrual, minutes,
   momentary, momently, monocot, monocotyl, monthly, newsmagazine,
   notebook, organ, pad, perennial, periodical, petty cashbook,
   pictorial, plant, pocket notebook, pocketbook, police blotter,
   polycot, polycotyl, polycotyledon, proceedings, quarterly,
   quotidian, report, returns, review, scrapbook, scratch pad,
   seasonal, secular, seed plant, seedling, semestral, semiannual,
   semimonthly, semiweekly, semiyearly, serial, slick magazine,
   spermatophyte, spiral notebook, sporophyte, statement, table,
   tablet, tally, tertian, thallophyte, the record, trade magazine,
   transactions, triennial, triptych, vascular plant, vegetable, weed,
   weekly, workbook, writing tablet, yearbook, yearly