momentous
adjective uk/məˈmen.təs/ us/məˈmen.t̬əs/
重大的，重要的
very important because of effects on future events
the momentous news of the president's death 总统去世的重大消息
Whether or not to move overseas was a momentous decision for the family. 是否移居海外对这个家庭来说是个重要的决定。