countdownn. 倒計數指示串聯中的運算元固定的記錄減少學術名詞遞減計數：電機工程、資訊倒數計時：電機工程倒數：航空太空倒計數：機械工程倒計時：機械工程英文釋義counting backward from an arbitrary number to indicate the time remaining before some event (such as launching a space vehicle)