1. Occurring every seven years.
2. Consisting of or continuing for seven years.
An event that occurs every seven years.

[From Late Latin septennium, period of seven years, from Latin septennis, of seven years : septem, seven; see septm̥ in Indo-European roots + annus, year; see at- in Indo-European roots.]

sep·ten′ni·al·ly adv.
References in periodicals archive ?
Such a belief, solely in the regulating merit of belief, is embodied not only in the Jewish booksread septennially, annually, monthly, weekly, dailybut also in books in general, if they are read not as commodities, rather as enduring resources (that timeless calendar, the canon).