The Collaborative International Dictionary of English v.0.48:

Alleviation \Al*le`vi*a"tion\, n. [LL. alleviatio.]
   1. The act of alleviating; a lightening of weight or
      severity; mitigation; relief.
      [1913 Webster]

   2. That which mitigates, or makes more tolerable.
      [1913 Webster]

            I have not wanted such alleviations of life as
            friendship could supply.              --Johnson.
      [1913 Webster]

WordNet (r) 3.0 (2006):

alleviation
    n 1: the feeling that comes when something burdensome is removed
         or reduced; "as he heard the news he was suddenly flooded
         with relief" [syn: relief, alleviation, assuagement]
    2: the act of reducing something unpleasant (as pain or
       annoyance); "he asked the nurse for relief from the constant
       pain" [syn: easing, easement, alleviation, relief]

Moby Thesaurus II by Grady Ward, 1.0:

80 Moby Thesaurus words for "alleviation":
   abatement, abridgment, allayment, analgesia, anesthesia,
   anesthetizing, appeasement, assuagement, attenuation, blunting,
   calming, contraction, dampening, damping, deadening, decrease,
   decrement, decrescence, deduction, deflation, demulsion,
   depreciation, depression, diminishment, diminution, disburdening,
   disencumberment, dulcification, dulling, dying, dying off, ease,
   easement, easing, extenuation, fade-out, falling-off, hushing,
   languishment, leniency, lessening, letdown, letup, lightening,
   loosening, lowering, lulling, miniaturization, mitigation,
   modulation, mollification, numbing, pacification, palliation,
   quietening, quieting, reduction, relaxation, relief, remedy,
   remission, sagging, salving, scaling down, simplicity, slackening,
   softening, soothing, subduement, subtraction, tempering,
   tranquilization, unballasting, unburdening, unfreighting, unlading,
   unloading, unsaddling, untaxing, weakening