The Collaborative International Dictionary of English v.0.48:

Reduce \Re*duce"\ (r[-e]*d[=u]s"), v. t. [imp. & p. p. Reduced
   (-d[=u]st"),; p. pr. & vb. n. Reducing (-d[=u]"s[i^]ng).]
   [L. reducere, reductum; pref. red-. re-, re- + ducere to
   lead. See Duke, and cf. Redoubt, n.]
   1. To bring or lead back to any former place or condition.
      [Obs.]
      [1913 Webster]

            And to his brother's house reduced his wife.
                                                  --Chapman.
      [1913 Webster]

            The sheep must of necessity be scattered, unless the
            great Shephered of souls oppose, or some of his
            delegates reduce and direct us.       --Evelyn.
      [1913 Webster]

   2. To bring to any inferior state, with respect to rank,
      size, quantity, quality, value, etc.; to diminish; to
      lower; to degrade; to impair; as, to reduce a sergeant to
      the ranks; to reduce a drawing; to reduce expenses; to
      reduce the intensity of heat. "An ancient but reduced
      family." --Sir W. Scott.
      [1913 Webster]

            Nothing so excellent but a man may fasten upon
            something belonging to it, to reduce it.
                                                  --Tillotson.
      [1913 Webster]

            Having reduced
            Their foe to misery beneath their fears. --Milton.
      [1913 Webster]

            Hester Prynne was shocked at the condition to which
            she found the clergyman reduced.      --Hawthorne.
      [1913 Webster]

   3. To bring to terms; to humble; to conquer; to subdue; to
      capture; as, to reduce a province or a fort.
      [1913 Webster]

   4. To bring to a certain state or condition by grinding,
      pounding, kneading, rubbing, etc.; as, to reduce a
      substance to powder, or to a pasty mass; to reduce fruit,
      wood, or paper rags, to pulp.
      [1913 Webster]

            It were but right
            And equal to reduce me to my dust.    --Milton.
      [1913 Webster]

   5. To bring into a certain order, arrangement,
      classification, etc.; to bring under rules or within
      certain limits of descriptions and terms adapted to use in
      computation; as, to reduce animals or vegetables to a
      class or classes; to reduce a series of observations in
      astronomy; to reduce language to rules.
      [1913 Webster]

   6. (Arith.)
      (a) To change, as numbers, from one denomination into
          another without altering their value, or from one
          denomination into others of the same value; as, to
          reduce pounds, shillings, and pence to pence, or to
          reduce pence to pounds; to reduce days and hours to
          minutes, or minutes to days and hours.
      (b) To change the form of a quantity or expression without
          altering its value; as, to reduce fractions to their
          lowest terms, to a common denominator, etc.
          [1913 Webster]

   7. (Chem.) To add an electron to an atom or ion.
      Specifically: To remove oxygen from; to deoxidize.
      (Metallurgy) To bring to the metallic state by separating
      from combined oxygen and impurities; as, metals are
      reduced from their ores. (Chem.) To combine with, or to
      subject to the action of, hydrogen or any other reducing
      agent; as, ferric iron is reduced to ferrous iron;
      aldehydes can be reduced to alcohols by lithium hydride;
      -- opposed to oxidize.
      [1913 Webster +PJC]

   8. (Med.) To restore to its proper place or condition, as a
      displaced organ or part; as, to reduce a dislocation, a
      fracture, or a hernia.
      [1913 Webster]

   Reduced iron (Chem.), metallic iron obtained through
      deoxidation of an oxide of iron by exposure to a current
      of hydrogen or other reducing agent. When hydrogen is used
      the product is called also iron by hydrogen.

   To reduce an equation (Alg.), to bring the unknown quantity
      by itself on one side, and all the known quantities on the
      other side, without destroying the equation.

   To reduce an expression (Alg.), to obtain an equivalent
      expression of simpler form.

   To reduce a square (Mil.), to reform the line or column
      from the square.
      [1913 Webster]

   Syn: To diminish; lessen; decrease; abate; shorten; curtail;
        impair; lower; subject; subdue; subjugate; conquer.
        [1913 Webster]

WordNet (r) 3.0 (2006):

reduce
    v 1: cut down on; make a reduction in; "reduce your daily fat
         intake"; "The employer wants to cut back health benefits"
         [syn: reduce, cut down, cut back, trim, trim
         down, trim back, cut, bring down]
    2: make less complex; "reduce a problem to a single question"
    3: bring to humbler or weaker state or condition; "He reduced
       the population to slavery"
    4: simplify the form of a mathematical equation of expression by
       substituting one term for another
    5: lower in grade or rank or force somebody into an undignified
       situation; "She reduced her niece to a servant"
    6: be the essential element; "The proposal boils down to a
       compromise" [syn: reduce, come down, boil down]
    7: reduce in size; reduce physically; "Hot water will shrink the
       sweater"; "Can you shrink this image?" [syn: shrink,
       reduce]
    8: lessen and make more modest; "reduce one's standard of
       living"
    9: make smaller; "reduce an image" [syn: reduce, scale down]
       [ant: blow up, enlarge, magnify]
    10: to remove oxygen from a compound, or cause to react with
        hydrogen or form a hydride, or to undergo an increase in the
        number of electrons [syn: deoxidize, deoxidise,
        reduce] [ant: oxidate, oxidise, oxidize]
    11: narrow or limit; "reduce the influx of foreigners" [syn:
        reduce, tighten]
    12: put down by force or intimidation; "The government quashes
        any attempt of an uprising"; "China keeps down her
        dissidents very efficiently"; "The rich landowners
        subjugated the peasants working the land" [syn: repress,
        quash, keep down, subdue, subjugate, reduce]
    13: undergo meiosis; "The cells reduce"
    14: reposition (a broken bone after surgery) back to its normal
        site
    15: destress and thus weaken a sound when pronouncing it
    16: reduce in scope while retaining essential elements; "The
        manuscript must be shortened" [syn: abridge,
        foreshorten, abbreviate, shorten, cut, contract,
        reduce] [ant: dilate, elaborate, enlarge, expand,
        expatiate, exposit, expound, flesh out, lucubrate]
    17: be cooked until very little liquid is left; "The sauce
        should reduce to one cup" [syn: boil down, reduce,
        decoct, concentrate]
    18: cook until very little liquid is left; "The cook reduced the
        sauce by boiling it for a long time" [syn: reduce, boil
        down, concentrate]
    19: lessen the strength or flavor of a solution or mixture; "cut
        bourbon" [syn: dilute, thin, thin out, reduce,
        cut]
    20: take off weight [syn: reduce, melt off, lose weight,
        slim, slenderize, thin, slim down] [ant: gain,
        put on]

Moby Thesaurus II by Grady Ward, 1.0:

404 Moby Thesaurus words for "reduce":
   abase, abash, abate, abbreviate, abrade, abridge, abstract,
   acetify, acidify, acidulate, adjust, adjust to, adulterate,
   afflict, alkalify, alkalize, allay, alleviate, allow, alter,
   analyze, anatomize, anesthetize, appease, apportion, assay,
   assimilate to, assuage, attemper, attenuate, bank the fire,
   bankrupt, baptize, bate, bear down, beat down, become, beggar,
   belittle, bend, benumb, blunt, bob, boil down, borate, box in,
   break, break down, break up, bring down, bring low, bring to,
   bring to terms, bump, bust, capsulize, carbonate, catalyze, change,
   change into, change over, charge off, chasten, cheapen, chemical,
   chlorinate, circumscribe, clip, coarct, compact, compress,
   concentrate, condense, condition, conquer, consolidate, constrain,
   constrict, constringe, contract, control, convert, couch, count,
   count calories, cramp, cripple, crop, crush, curtail, cushion, cut,
   cut back, cut down, cut off short, cut prices, cut short, damp,
   dampen, de-emphasize, deaden, deaden the pain, debase, debilitate,
   decline, decrease, deduct, deflate, degrade, demean, demote,
   deplume, depreciate, depress, derange, derogate, detract, detrude,
   devaluate, devitalize, diet, dilute, diminish, disable, discount,
   disgrade, disorder, disparage, displume, dissect, distill, dive,
   divide, do over, dock, downbear, downgrade, downplay, drain, draw,
   draw in, draw together, drop, dull, dump, dump on, ease,
   ease matters, eat away, electrolyze, elide, enervate, enfeeble,
   epitomize, erode, eviscerate, exhaust, extenuate, extract, fall,
   fall in price, fell, ferment, file away, fix, flatten, foment,
   foreshorten, give relief, give way, grind, gruel, haul down, hedge,
   hedge about, homopolymerize, hospitalize, humble, humiliate,
   hydrate, hydrogenate, hydroxylate, impair, impoverish, increase,
   indent, indispose, invalid, irrigate, isomerize, jew down,
   keep within bounds, kick back, knit, knock down, lay, lay low,
   lay up, leach, leaven, lenify, lessen, let down, let up on,
   lighten, limit, lose flesh, lose weight, lower, lull, make,
   make allowance, make over, mark down, master, measure, minimize,
   mitigate, moderate, modify, modulate, mollify, mow, narrow,
   naturalize, nip, nitrate, nose-dive, numb, number, obtund,
   overmaster, override, oversimplify, overwhelm, oxidize, pad,
   palliate, parcel, pare, pauperize, pepsinate, peroxidize,
   phosphatize, play down, plummet, plunge, poll, pollard, polymerize,
   poultice, pour balm into, pour oil on, powder, press down,
   prostrate, prune, pucker, pucker up, pull down, pulp, purify,
   purse, push down, put down, qualify, quantify, quantize, quell,
   rarefy, rate, rattle, reap, rebate, recap, recapitulate, reconvert,
   reduce the temperature, reduce to, reduce to elements,
   reduce weight, refine, refund, regulate by, relieve, remove,
   render, reset, resolve, resolve into, restrain, restrict, retrench,
   reverse, ride down, roll back, rub, rub away, sag, salve, sap,
   scale down, season, segment, separate, set, set conditions,
   set down, set limits, shake, shake up, shave, shear, shift,
   shorten, sicken, simplify, sink, slacken, slake, slash, slenderize,
   slim, slim down, slow down, slump, smash, smother, snub, sober,
   sober down, soften, soften up, solidify, soothe, step down, stifle,
   strangle, strangulate, streamline, strip down, strip of rank,
   stunt, stupe, subdivide, subduct, subdue, subjugate, subtract,
   sulfate, sulfatize, sulfonate, sum up, summarize, suppress, switch,
   switch over, synopsize, take a premium, take away, take down,
   take from, take in, take off, take off weight, tame, telescope,
   temper, thin, thin down, thin out, thrust down, tone down,
   trample down, trample underfoot, transform, tread underfoot, trim,
   trip up, triturate, truncate, tune down, turn, turn back,
   turn into, tyrannize, unbrace, undermine, underplay, unman,
   unnerve, unstrengthen, unstring, vanquish, water, water down,
   weaken, wear away, weed, weight-watch, withdraw, work, wrinkle,
   write off



The Free On-line Dictionary of Computing (30 December 2018):

REDUCE

    A symbolic mathematics language with
   ALGOL-like syntax, written in Lisp by Anthony Hearn in
   1963.

   Reduce 2 is a version based on Portable Standard LISP.

   (http://rrz.uni-koeln.de/REDUCE/).

   E-mail: .

   Server: reduce-netlib@rand.org.

   ["REDUCE, Software for Algebraic Computation", G. Rayna,
   Springer 1987].

   (1994-10-31)