novennial

From novennium (“9-year period”) + -al, q.v.

novennial (not comparable)

1. Of or relating to a 9-year period.

• enneaeteric, enneatic

• “novennial, adj.”, in OED Online ⁠, Oxford: Oxford University Press, 2022.
• “novennial”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.