quadrennial Syllabification: (quad·ren·ni·al)Pronunciation: /kwäˈdrenēəl/Definition of quadrennial adjective recurring every four years. lasting for or relating to a period of four years. Derivatives quadrennially adverb Origin: mid 17th century: from quadrennium + -alquadrennial in other Oxford dictionaries Definition of quadrennial in the British & World English dictionary