Source : Webster's Revised Unabridged Dictionary (1913)

Parapet \Par"a*pet\, n. [F., fr. It. parapetto, fr. parare to
   ward off, guard (L. parare to prepare, provide) + petto the
   breast, L. pectus. See {Parry}, and {Pectoral}.]
   1. (Arch.) A low wall, especially one serving to protect the
      edge of a platform, roof, bridge, or the like.

   2. (Fort.) A wall, rampart, or elevation of earth, for
      covering soldiers from an enemy's fire; a breastwork. See
      Illust. of {Casemate}.

Source : WordNet®

parapet
     n 1: a low wall along the edge of a roof or balcony
     2: fortification consisting of a low wall [syn: {breastwork}]