The Collaborative International Dictionary of English v.0.48:

Acroterium \Ac`ro*te`ri*um\ (-[u^]m), n.; pl. Acroteria. [L.,
   fr. Gr. 'akrwth`rion summit, fr. 'a`kros topmost.] (Arch.)
   (a) One of the small pedestals, for statues or other
       ornaments, placed on the apex and at the basal angles of
       a pediment. Acroteria are also sometimes placed upon the
       gables in Gothic architecture. --J. H. Parker.
   (b) One of the pedestals, for vases or statues, forming a
       part roof balustrade.
       [1913 Webster]