1. Counting backward from an arbitrary number to indicate the time remaining before some event (such as launching a space vehicle)
   "The excited crowd joined in the countdown to midnight on New Year's Eve"

1. Count backwards; before detonating a bomb, for example
   "The mission control centre counted down to the rocket launch"

Derived forms: counted down, countdowns, counts down, counting down

See also: count

Type of: count, counting, enumeration, numeration, reckoning, tally

Encyclopedia: Countdown