The Collaborative International Dictionary of English v.0.48:

Subdue \Sub*due"\, v. t. [imp. & p. p. Subdued; p. pr. & vb.
   n. Subduing.] [OE. soduen, OF. sosduire to seduce, L.
   subtus below (fr. sub under) + ducere to lead. See Duke,
   and cf. Subduct.]
   1. To bring under; to conquer by force or the exertion of
      superior power, and bring into permanent subjection; to
      reduce under dominion; to vanquish.
      [1913 Webster]

            I will subdue all thine enemies.      --1 Chron.
                                                  xvii. 10.
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   2. To overpower so as to disable from further resistance; to
      crush.
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            Nothing could have subdued nature
            To such a lowness, but his unkind daughters. --Shak.
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            If aught . . . were worthy to subdue
            The soul of man.                      --Milton.
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   3. To destroy the force of; to overcome; as, medicines subdue
      a fever.
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   4. To render submissive; to bring under command; to reduce to
      mildness or obedience; to tame; as, to subdue a stubborn
      child; to subdue the temper or passions.
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   5. To overcome, as by persuasion or other mild means; as, to
      subdue opposition by argument or entreaties.
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   6. To reduce to tenderness; to melt; to soften; as, to subdue
      ferocity by tears.
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   7. To make mellow; to break, as land; also, to destroy, as
      weeds.
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   8. To reduce the intensity or degree of; to tone down; to
      soften; as, to subdue the brilliancy of colors.
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   Syn: To conquer; overpower; overcome; surmount; vanquish. See
        Conquer.
        [1913 Webster]

WordNet (r) 3.0 (2006):

subdue
    v 1: 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]
    2: to put down by force or authority; "suppress a nascent
       uprising"; "stamp down on littering"; "conquer one's desires"
       [syn: suppress, stamp down, inhibit, subdue,
       conquer, curb]
    3: hold within limits and control; "subdue one's appetites";
       "mortify the flesh" [syn: mortify, subdue, crucify]
    4: get on top of; deal with successfully; "He overcame his
       shyness" [syn: overcome, get over, subdue, surmount,
       master]
    5: make subordinate, dependent, or subservient; "Our wishes have
       to be subordinated to that of our ruler" [syn: subordinate,
       subdue]
    6: correct by punishment or discipline [syn: tame, chasten,
       subdue]

Moby Thesaurus II by Grady Ward, 1.0:

184 Moby Thesaurus words for "subdue":
   abate, allay, alleviate, anesthetize, appease, asphyxiate, assuage,
   attemper, baffle, bank the fire, bear down, beat down, bend,
   benumb, blunt, bottle up, break, break down, bridle, bring low,
   bring to terms, calm, calm down, censor, chasten, check, choke off,
   clamp down on, compose, conquer, constrain, control, cool, cork,
   cork up, crack down on, cradle, crush, curb, cushion, damp,
   damp down, dampen, de-emphasize, deaden, deaden the pain, deafen,
   defeat, diminish, dominate, downplay, drown, dulcify, dull, ease,
   ease matters, even out, extenuate, extinguish, fell, flatten,
   fluff, foment, gag, gentle, give relief, hold down, hold in check,
   humble, humiliate, hush, jump on, keep down, keep in check,
   keep under, keep within bounds, kill, knead, laxate, lay, lenify,
   lessen, lighten, limber, limber up, loosen, lull, mash, massage,
   master, mellow, milden, mitigate, moderate, modulate, mollify,
   muffle, mute, muzzle, numb, obtund, overcome, overmaster,
   overpower, override, overwhelm, pacify, pad, palliate, play down,
   plump, poultice, pour balm into, pour oil on, pour water on,
   prostrate, pulp, put down, quash, quell, quench, quiet, reduce,
   reduce the temperature, relax, relieve, repress, rest, restrain,
   ride down, rock, rock to sleep, salve, shake up, shut down on,
   silence, sit down on, sit on, slacken, slake, slow down, smash,
   smooth, smooth down, smooth over, smoothen, smother, sober,
   sober down, soft-pedal, soften, soften up, soothe, squash, squelch,
   stabilize, stanch, steady, stifle, still, stop, strangle, stultify,
   stupe, subjugate, suffocate, supple, suppress, tame, temper,
   tenderize, throttle, tone down, trample down, trample underfoot,
   tranquilize, tread underfoot, triumph over, tune down, tyrannize,
   underplay, unman, vanquish, weaken