septcentenaryPronunciation: /ˌsɛp(t)sɛnˈtiːn(ə)ri, -ˈtɛn-/Definition of septcentenary noun (plural septcentenaries) the seven-hundredth anniversary of a significant event. adjective relating to a seven-hundredth anniversary. septcentenary in other Oxford dictionaries Definition of septcentenary in the US English dictionary