(ˈ)sek|senēəl adjective
Etymology: Latin sexenni um period of six years (from sex six + -ennium, from annus year) + English -al — more at six , annual
1. : continuing or lasting six years
a sexennial period
2. : occurring, appearing, or being made, done, or acted upon every six years
• sex·en·ni·al·ly -əlē, -li adverb