Idiom
before you can say somethingbefore you can say (something)
surprisingly quickly.This bow shoots so fast, the arrow is in the target before you can say “gee whiz!”
Usage notes: often the word or phrase that follows before you can say is related to the situation you are talking about:
In summer, food goes bad before you can say “heat wave!”
Etymology: an older form of this expression is before you can say Jack Robinson