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

Roget 284: propulsion, projection; propelment^†; vis a tergo [Lat.], force from behind; push, shove etc. (impulse) 276; ejaculate; ejection etc. 297; throw, fling, toss, shot, discharge, shy; launch, release.    [Science of propulsion] projectiles, ballistics, archery.    [devices to give propulsion] propeller, screw, twin screws, turbine, jet engine.    [objects propelled] missile, projectile, ball, discus, quoit, brickbat, shot; [weapons which propel] arrow, gun, ballista etc. (arms) 727^†.    [preparation for propulsion] countdown, windup.    shooter; shot; archer, toxophilite^†; bowman, rifleman, marksman; good shot, crack shot; sharpshooter etc. (combatant) 726.    ... show more

Dutch: aftelling, aftelprocedure, aftellen, countdown