The Collaborative International Dictionary of English v.0.48:

Ameliorate \A*mel"io*rate\, v. t. [imp. & p. p. Ameliorated;
   p. pr. & vb. n. Ameliorating.] [L. ad + meliorare to make
   better: cf. F. am['e]liorer. See Meliorate.]
   To make better; to improve; to meliorate.
   [1913 Webster]

         In every human being there is a wish to ameliorate his
         own condition.                           --Macaulay.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

ameliorating \ameliorating\ adj. prenom. [p. pr. of
   ameliorate.]
   causing improvement in or reducing the bad effects of an
   unfavorable condition.

   Syn: ameliorative, amelioratory, meliorative
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

ameliorating
    adj 1: tending to ameliorate [syn: ameliorating(a),
           ameliorative, amelioratory, meliorative]