Undecennary
Pronunciation : Un`de*cen"na*ry
Part of Speech : a.
Etymology : [L. undecim eleven (unus one + decem ten) + -ennary as in decennary. Cf. Undecennial.]
Definition : Defn: Occurring once in every period of eleven years; undecennial. An undecennary account laid before Parliament. E. Stiles.
Source : Webster's Unabridged Dictionary, 1913