Source : Webster's Revised Unabridged Dictionary (1913)

Scalper \Scalper\ (sk[a^]lp"[~e]r), n.
   1. One who, or that which, scalps.

   2. (Surg.) Same as {Scalping iron}, under {Scalping}.

   3. A broker who, dealing on his own account, tries to get a
      small and quick profit from slight fluctuations of the
      market. [Cant]

   4. A person who buys and sells the unused parts of railroad
      tickets. [Cant]

Source : WordNet®

scalper
     n : someone who buys something and resells it at a price far
         above the initial cost; "he got theater tickets through a
         scalper"