Source : Webster's Revised Unabridged Dictionary (1913)

Ameliorative \A*mel"io*ra*tive\, a.
   Tending to ameliorate; producing amelioration or improvement;
   as, ameliorative remedies, efforts.

Source : WordNet®

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