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®

mercifulness
     n 1: the feeling that motivates compassion [syn: {mercy}]
     2: a disposition to be kind and forgiving; "in those days a
        wife had to depend on the mercifulness of her husband"
        [syn: {mercy}] [ant: {mercilessness}]
     3: leniency and compassion shown toward offenders by a person
        or agency charged with administering justice; "he threw
        himself on the mercy of the court" [syn: {clemency}, {mercy}]