The Collaborative International Dictionary of English v.0.48:

Head-hunter \Head"-hunt`er\ (h[e^]d"h[u^]nt`[~e]r), n.
   A member of any tribe or race of savages who have the custom
   of decapitating human beings and preserving their heads as
   trophies. The Dyaks of Borneo are the most noted
   head-hunters.
   [1913 Webster]

   2. A person whose profession is to find executives to fill
      open positions in corporations; an executive personnel
      recruiter; also, a company that performs a similar
      service.
      [PJC] -- Head"-hunt`ing, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

headhunter
    n 1: a recruiter of personnel (especially for corporations)
    2: a savage who cuts off and preserves the heads of enemies as
       trophies [syn: headhunter, head-shrinker]