复数:d-days
1.(第二次世界大战中盟军在西欧发起反攻的)反攻日
2.(一般的)攻击发起日
3.十进日
1.June 6, 1944, the day on which the U.S., British, and other armies arrived on the beaches of northern France in World War II
2.the day when something important happens, usually something that you have been planning for a long time