1. the act of counting backward to zero, especially before the launch of a rocket or the start of an event
2. a period of time leading up to an important event

1. to count backward to zero

Examples

• The rocket launch began with a ten-second countdown.
• We watched the New Year’s countdown on television.
• The countdown to the election has begun.
• There’s a countdown timer on the website showing days until the sale ends.
• The announcer started to countdown from five.
• Mission control will countdown to liftoff.
• The final countdown before the concert made everyone excited.