Source : Webster's Revised Unabridged Dictionary (1913)

Machicolation \Mach`i*co*la"tion\, n. [Cf. LL. machicolamentum,
   machacolladura, F. m[^a]chicolis, m[^a]checoulis; perh. fr.
   F. m[`e]che match, combustible matter + OF. coulis, couleis,
   flowing, fr. OF. & F. couler to flow. Cf. {Match} for making
   fire, and {Cullis}.]
   1. (Mil. Arch.) An opening between the corbels which support
      a projecting parapet, or in the floor of a gallery or the
      roof of a portal, shooting or dropping missiles upen
      assailants attacking the base of the walls. Also, the
      construction of such defenses, in general, when of this
      character. See Illusts. of {Battlement} and {Castle}.

   2. The act of discharging missiles or pouring burning or
      melted substances upon assailants through such apertures.

Source : WordNet®

machicolation
     n : a projecting parapet supported by corbels on a medieval
         castle; has openings through which stones or boiling
         water could be dropped on an enemy