Octennial
Pronunciation : Oc*ten"ni*al
Part of Speech : a.
Etymology : [L. octennium a period of eight years; octo eight + annus year.]
Definition : Defn: Happening every eighth year; also, lasting a period of eight years. Johnson. -- Oc*ten"ni*al*ly, adv.
Source : Webster's Unabridged Dictionary, 1913