Octennial a. : Happening every eighth year; also, lasting a period of eight years.

Example:


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Defination from the web:
Octennial in the Online Dictionary. Meaning of Octennial. Pronunciation of Octennial. Translations of Octennial. Octennial synonyms, Octennial antonyms. ... Of late these shackles, if I mistake not, have been broken; and octennial parliaments have besides been established. ...