COUNTDOWN

n. . Space English , informal 1. A step-by-step process which leads to the launching of a rocket. Countdown starts at 23:00 hours tomorrow night and continues for 24 hours. 2. Process of counting inversely during the acts leading to a launch; liftoff occurs at zero. 3. The time immediately preceding an important undertaking, borrowed from Space English. We're leaving for Hawaii tomorrow afternoon; this is countdown time for us.