Definition of septennium in US English:

septennium

noun

rare
  • A specified period of seven years.

    • ‘This septennium must designate something peculiar and different from the time following.’
    • ‘In Wurtemburg the fall has been somewhat less striking, the mortality rates for the two septennia and for the year 1894 being 199, 107, and 104 respectively.’

Origin

Mid 19th century: from late Latin, from Latin septem ‘seven’ + annus ‘year’.

Pronunciation

septennium

/sepˈtenēəm/