Source : Webster's Revised Unabridged Dictionary (1913)

Kidnaper \Kid"nap`er\, or Kidnapper \Kid"nap`per\, n.
   One who steals or forcibly carries away a human being; a
   manstealer.

Source : WordNet®

kidnapper
     n : someone who unlawfully seizes and detains a victim (usually
         for ransom) [syn: {abductor}, {snatcher}]