N-SING
(尤指航天器發射前的)倒計時
A countdown is the counting aloud of numbers in reverse order before something happens, especially before a spacecraft is launched.
例句
The countdown has begun for the launch later today of the American space shuttle...
美國航天飛機的發射已于今天晚些時候開始進入倒計時。
There were three more things to do before countdown.
開始倒計時之前還有3件事要做。