Countdown and Runup

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

Runup and countdown are semantically related In some cases you can replace term "Runup" with "Countdown", this nouns are similar.

Nearby Words: count, counting

Runup noun - A substantial increase over a relatively short period of time.

Countdown and runup are semantically related in short preliminary event topic. You can use "Countdown" instead a noun "Runup".