The Collaborative International Dictionary of English v.0.48:

Empalement \Em*pale"ment\, n. [Cf. F. empalement, fr. empaler.
   See Empale.] [Written also impalement.]
   1. A fencing, inclosing, or fortifying with stakes.
      [1913 Webster]

   2. A putting to death by thrusting a sharpened stake through
      the body.
      [1913 Webster]

   3. (Her.) Same as Impalement.
      [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

EMPALEMENT. A punishment in which a sharp polo was forced up the fundament.
Encyc. Lond. h.t.