Source : Webster's Revised Unabridged Dictionary (1913)

Pediment \Ped"i*ment\, n. [L. pes, pedis, a foot. See {Foot}.]
   (Arch.)
   Originally, in classical architecture, the triangular space
   forming the gable of a simple roof; hence, a similar form
   used as a decoration over porticoes, doors, windows, etc.;
   also, a rounded or broken frontal having a similar position
   and use. See {Temple}.

Source : WordNet®

pediment
     n : a triangular gable between a horizontal entablature and a
         sloping roof