The Collaborative International Dictionary of English v.0.48:

Decastere \Dec"a*stere\, n. [L. d['e]cast[`e]re; Gr. de`ka ten +
   F. st[`e]re a stere.] (Metric System)
   A measure of capacity, equal to ten steres, or ten cubic
   meters.
   [1913 Webster]