The Collaborative International Dictionary of English v.0.48:

Alleviate \Al*le"vi*ate\, v. t. [imp. & p. p. Alleviated; p.
   pr. & vb. n. Alleviating.] [LL. alleviare, fr. L. ad +
   levis light. See Alegge, Levity.]
   1. To lighten or lessen the force or weight of. [Obs.]
      [1913 Webster]

            Should no others join capable to alleviate the
            expense.                              --Evelyn.
      [1913 Webster]

            Those large bladders . . . conduce much to the
            alleviating of the body [of flying birds]. --Ray.
      [1913 Webster]

   2. To lighten or lessen (physical or mental troubles); to
      mitigate, or make easier to be endured; as, to alleviate
      sorrow, pain, care, etc.; -- opposed to aggravate.
      [1913 Webster]

            The calamity of the want of the sense of hearing is
            much alleviated by giving the use of letters. --Bp.
                                                  Horsley.
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   3. To extenuate; to palliate. [R.]
      [1913 Webster]

            He alleviates his fault by an excuse. --Johnson.
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   Syn: To lessen; diminish; soften; mitigate; assuage; abate;
        relieve; nullify; allay.

   Usage: To Alleviate, Mitigate, Assuage, Allay. These
          words have in common the idea of relief from some
          painful state; and being all figurative, they differ
          in their application, according to the image under
          which this idea is presented. Alleviate supposes a
          load which is lightened or taken off; as, to alleviate
          one's cares. Mitigate supposes something fierce which
          is made mild; as, to mitigate one's anguish. Assuage
          supposes something violent which is quieted; as, to
          assuage one's sorrow. Allay supposes something
          previously excited, but now brought down; as, to allay
          one's suffering or one's thirst. To alleviate the
          distresses of life; to mitigate the fierceness of
          passion or the violence of grief; to assuage angry
          feeling; to allay wounded sensibility.
          [1913 Webster]

WordNet (r) 3.0 (2006):

alleviate
    v 1: provide physical relief, as from pain; "This pill will
         relieve your headaches" [syn: relieve, alleviate,
         palliate, assuage]
    2: make easier; "you could facilitate the process by sharing
       your knowledge" [syn: facilitate, ease, alleviate]

Moby Thesaurus II by Grady Ward, 1.0:

88 Moby Thesaurus words for "alleviate":
   abate, allay, anesthetize, appease, assuage, attemper, attenuate,
   bank the fire, bate, be light, benumb, blunt, chasten, constrain,
   control, cure, cushion, damp, dampen, de-emphasize, deaden,
   deaden the pain, dilute, diminish, disburden, disencumber,
   downplay, dull, ease, ease matters, extenuate, foment, give relief,
   have little weight, keep within bounds, kick the beam, lay, lenify,
   lessen, lighten, lull, make light, make lighter, mitigate,
   moderate, modulate, mollify, numb, obtund, off-load, pad, palliate,
   play down, poultice, pour balm into, pour oil on, reduce,
   reduce the temperature, reduce weight, relieve, remedy, remit,
   restrain, salve, slacken, slake, slow down, smother, sober,
   sober down, soften, soothe, stifle, stupe, subdue, suppress, tame,
   temper, tone down, tune down, unballast, unburden, underplay,
   unlade, unload, water down, weaken, weigh lightly