'Decuman' definitions:

Definition of 'Decuman'

From: GCIDE

Decuman \Dec"u*man\, a. [L. decumanus of the tenth, and by metonymy, large, fr. decem ten.] Large; chief; -- applied to an extraordinary billow, supposed by some to be every tenth in order. [R.] Also used substantively. "Such decuman billows." --Gauden. "The baffled decuman." --Lowell.