The Collaborative International Dictionary of English v.0.48:

Subdued \Sub*dued"\, a.
   1. Conquered; overpowered; crushed; submissive; mild.
      [1913 Webster]

   2. Not glaring in color; soft in tone.
      [1913 Webster]

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.
      [1913 Webster]

   2. To overpower so as to disable from further resistance; to
      crush.
      [1913 Webster]

            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.
      [1913 Webster]

   3. To destroy the force of; to overcome; as, medicines subdue
      a fever.
      [1913 Webster]

   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.
      [1913 Webster]

   5. To overcome, as by persuasion or other mild means; as, to
      subdue opposition by argument or entreaties.
      [1913 Webster]

   6. To reduce to tenderness; to melt; to soften; as, to subdue
      ferocity by tears.
      [1913 Webster]

   7. To make mellow; to break, as land; also, to destroy, as
      weeds.
      [1913 Webster]

   8. To reduce the intensity or degree of; to tone down; to
      soften; as, to subdue the brilliancy of colors.
      [1913 Webster]

   Syn: To conquer; overpower; overcome; surmount; vanquish. See
        Conquer.
        [1913 Webster]

WordNet (r) 3.0 (2006):

subdued
    adj 1: in a softened tone; "hushed voices"; "muted trumpets"; "a
           subdued whisper"; "a quiet reprimand" [syn: hushed,
           muted, subdued, quiet]
    2: restrained in style or quality; "a little masterpiece of low-
       keyed eloquence" [syn: low-key, low-keyed, subdued]
    3: quieted and brought under control; "children were subdued and
       silent"
    4: not brilliant or glaring; "the moon cast soft shadows"; "soft
       pastel colors"; "subdued lighting" [syn: soft, subdued]
    5: lacking in light; not bright or harsh; "a dim light beside
       the bed"; "subdued lights and soft music" [syn: dim,
       subdued]

Moby Thesaurus II by Grady Ward, 1.0:

212 Moby Thesaurus words for "subdued":
   Attic, Olympian, aesthetic, aloof, artistic, backward,
   barely audible, bashful, bated, blank, bowed-down, broken,
   brought low, calmed, cast down, chaste, chastened, chilled, chilly,
   choice, classic, cold, conquered, constrained, controlled, cool,
   creamy, crestfallen, crushed, damped, dampened, dashed, dead,
   deadened, decrescendo, dejected, delicate, depressed, despairing,
   despondent, desponding, detached, dim, discouraged, discreet,
   disheartened, dispirited, distant, domesticated, dovelike, down,
   downcast, downhearted, drooping, droopy, dull, dulled, eggshell,
   excellent, expressionless, faint, faint-voiced, feeble,
   feeling low, felled, flat, flattened, forbidding, frigid, frosty,
   gentle, gloss, grave, guarded, half-heard, heartless, housebroke,
   housebroken, humble, humbled, humiliated, hushed, hypochondriac,
   hypochondriacal, icy, impassive, impersonal, in control,
   in good taste, in hand, in low spirits, in the depths,
   in the doldrums, in the dumps, inaccessible, indistinct,
   introverted, iridescent, lamblike, languishing, light, limited,
   low, low-key, low-spirited, made to grovel, mastered, meek, mellow,
   mellowed, mild, moderated, modest, mother-of-pearl, muffled,
   murmured, muted, nacreous, of choice, of quality, offish,
   opalescent, pacific, pale, pastel, patinaed, peaceable, peaceful,
   pearly, pessimistic, pianissimo, piano, pining, placid, pleasing,
   pure, put down, quashed, quelled, quiet, reduced, remote, removed,
   repressed, reserved, restrained, reticent, retiring, sad, saddened,
   scarcely heard, semigloss, serious, shrinking, simple, smashed,
   smothered, sober, sobered, soft, soft-colored, soft-hued,
   soft-sounding, soft-voiced, softened, solemn, somber, sordo,
   spiritless, squashed, squelched, stable, standoff, standoffish,
   stifled, subaudible, subjugated, submissive, subtle, suffocated,
   suicidal, suppressed, sweet, tame, tamed, tasteful, tasty,
   temperate, tempered, tender, toned, tranquil, unaffable,
   unaffected, unapproachable, unclear, uncongenial, undemonstrative,
   understated, unenthusiastic, unexpansive, ungenial, unobtrusive,
   vanquished, weak, weak-voiced, weary of life, well-chosen,
   whispered, withdrawn, woebegone, world-weary