The Collaborative International Dictionary of English v.0.48:
Kidnaper \Kid"nap`er\ (k[i^]d"n[a^]p`[~e]r), or Kidnapper \Kid"nap`per\, n. One who steals or forcibly carries away a human being; a manstealer. [1913 Webster]WordNet (r) 3.0 (2006):
kidnapper n 1: someone who unlawfully seizes and detains a victim (usually for ransom) [syn: kidnapper, kidnaper, abductor, snatcher]