unprecedented/ʌnˈpresɪdentɪd/
adj.空前的；没有前例的The enemy mad bombardment caused unprecedented death and destruction in the country.敌人的狂轰滥炸在这个国家造成了空前的死亡和破坏。
The early 90's finds an unprecedented tide of rural workers flooding into big cities in China.九十年代初期，一股历史上从未有过的农民工的潮流涌进了中国的大城市。