Lewis & Short

castellānus, a, um, adj. [castellum],

  1. I. of or pertaining to a fort or castle: triumphi, for the capture of a castle, * Cic. Brut. 73, 256: miles, Cod. Th. 7, 15, 2.
  2. II. As subst.: castellāni, ōrum, m., the occupants of a castle, Sall. J. 92, 7; Hirt. B. Alex. 42, 3; Liv 34, 27, 2; 38, 45, 9.