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.是什么意思_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.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句