Source : Webster's Revised Unabridged Dictionary (1913)

Merciful \Mer"ci*ful\, a. [Mercy + -ful.]
   1. Full of mercy; having or exercising mercy; disposed to
      pity and spare offenders; unwilling to punish.

            The Lord, the Lord God, merciful and gracious. --Ex.
                                                  xxxiv. 6.

            Be merciful, great duke, to men of mold. --Shak.

   2. Unwilling to give pain; compassionate.

            A merciful man will be merciful to his beast. --Old
                                                  Proverb.

   Syn: Compassionate; tender; humane; gracious; kind; mild;
        clement; benignant. -- {Mer"ci*ful*ly}, adv. --
        {Mer"ci*ful*ness}, n.

Source : WordNet®

mercifully
     adv 1: in a manner that may be cruel but avoids suffering; "we more
            mercifully had our bouncing betties go off at the
            head"
     2: in a compassionate manner; "he dealt with the thief
        mercifully" [syn: {with mercy}, {showing mercy}]