Source : Webster's Revised Unabridged Dictionary (1913)

Cymatium \Cy*ma"ti*um\ (s[i^]*m[=a]"sh[i^]*[u^]m), n. [L., fr.
   Gr. kyma`tion, dim. of ky^ma a wave.] (Arch.)
   A capping or crowning molding in classic architecture.

Source : WordNet®

cymatium
     n : (architecture) a molding for a cornice; in profile it is
         partly concave and partly convex [syn: {cyma}]
     [also: {cymatia} (pl)]