Lewis & Short

quinquāgēnārĭus, a, um, adj. [quinquageni].

  1. I. Consisting of fifty, containing fifty: grex equarum, Varr. R. R. 2, 10, 11: dolium, Cato, R. R. 69, 2: urna, id. ib. 10, 2: fistula, the plate of which, before being bent, was fifty inches in width, Vitr. 8, 7: quinquagenarius (homo), fifty years old, Quint. 9, 2, 85.
  2. II. Subst.: quinquāgēnārĭi, among the Israelites, military officers commanding fifty men, captains over fifty, Hier. in Isa. 2, 3, 3; Vulg. Exod. 18, 21; id. Deut. 1, 15; id. 1 Reg. 1, 9 sq.