Lewis Short
(adjective) : sĕcundānus, a, um, secundus; in gen.
* The second in rank or order (postclass.): Juppiter,i. e. Neptune,Mart. Cap. 1, § 47: Pales,id. ib. 1, § 51.—Plur. as subst.: sĕcundāni, ōrum, m. (sc. milites), soldiers of the second legion (like primani, tertiani, decimani, etc.): secundani terga hostium caedunt (preceded by secundae legionis principes hastatique),Liv. 34, 15 fin.; 34, 46 fin.; 41, 3; Tac. H. 5, 16; Plin. 3, 4, 5, § 36.
Charlton T. Lewis, Charles Short, A Latin Dictionary