Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sĕcundānus, a, um, adj. [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.