decuman /ˈdɛkjʊmən/adjective 2noun 1forms 1 adjective2 •(historical) Connected with the principal gate of an Ancient Roman camp, near which the tenth cohort of the legion was stationed. •(no longer used) Large; chief; applied to an extraordinary billow, supposed by some to be every tenth in sequence.decuman billows — 1870 noun1 •(no longer used) An extraordinarily large billow. formsdecumans
