单词：countdowns
音标：[ˈkaʊntˌdaʊnz] ；
n. （发射宇宙飞船等的）倒数读秒, 倒计时( countdown的复数形式 ); 大事临近的时期
n. counting backward from an arbitrary number to indicate the time remaining before some event (such as launching a space vehicle)