Lewis & Short

septĭmānus, a, um, adj. [septem].

  1. I. Of or belonging to the number seven: Nonae, falling on the seventh day of the month (in March, May, July, and October; opp. quintanae, which fell upon the fifth day), Varr. L. L. 6, § 27 Müll.; Macr. S. 1, 14; Censor. de Die Nat. 20: feturae, born in the seventh month, Arn. 3, 105.
  2. II. Subst.
    1. A. septĭmāni, ōrum, m., soldiers of the seventh legion, Plin. 3, 4, 5, § 36; Tac. H. 3, 25.
    2. B. septĭmāna, ae, f., late Lat. for hebdomas, a week, Cod. Th. 15, 5, 5: die septimanarum, the Jewish feast of weeks, Vulg. 2 Macc. 12, 31.
      Hence, septĭmā-nărĭi, = hebdomadarii, Reg. Bened. 35.