Wiktionary
count down
n. (alternative spelling of countdown English) vb. 1 To announce the passage of time to a precisely timed expected event. 2 To await a precisely timed expected event.
WordNet
count down
v. count backwards; before detonating a bomb, for example
Usage examples of "count down".
Now he stands in a lobby of the Foote Mansion, watching electric numbers above an elevator count down, occasionally sneaking a glance at himself in a big mirror.