名詞 countdown:

1. counting backward from an arbitrary number to indicate the time remaining before some event (such as launching a space vehicle)

count.down

n.（名詞）
The counting backward aloud from an arbitrary starting number to indicate the time remaining before an event or operation, such as the launching of a missile or space vehicle.
倒數(shù)報(bào)時(shí)：從任意的一個(gè)數(shù)字開(kāi)始倒著數(shù)，以表明距離某件事或操作（例如發(fā)射導(dǎo)彈或宇宙飛船）的時(shí)間
The checks and preparations carried out during this activity.
準(zhǔn)備過(guò)程，準(zhǔn)備工作：在倒數(shù)報(bào)時(shí)期間所進(jìn)行的檢查和準(zhǔn)備