資料來源 : Webster's Revised Unabridged Dictionary (1913)

Merciless \Mer"ci*less\, a.
   Destitute of mercy; cruel; unsparing; -- said of animate
   beings, and also, figuratively, of things; as, a merciless
   tyrant; merciless waves.

         The foe is merciless, and will not pity. --Shak.

   Syn: Cruel; unmerciful; remorseless; ruthless; pitiless;
        barbarous; savage. -- {Mer"ci*less*ly}, adv. --
        {Mer"ci*less*ness}, n.

資料來源 : WordNet®

mercilessness
     n 1: feelings of extreme heartlessness [syn: {cruelty}, {pitilessness},
           {ruthlessness}]
     2: inhumaneness evidenced by an unwillingness to be kind or
        forgiving [syn: {unmercifulness}] [ant: {mercifulness}]