D defs.my
Entry 1 sense Webster, 1913

Undecennary

· Un·de·cen·na·ry · IPA
01 a. Occurring once in every period of eleven years; undecennial.
  1. 1.
    Occurring once in every period of eleven years; undecennial.
    “An undecennary account laid before Parliament.” — E. Stiles.