be quick/slow off the mark
be quick off the mark
To be quick to react or take action. You have to be quick off the mark if you're going to be an emergency responder.
be slow off the mark
To be slow to react or take action. He's too slow off the mark to be an effective emergency responder. You were a little slow off the mark on your last line. Come in a little bit sooner next time.
be quick (or slow) off the markbe fast (or slow) in responding to a situation or understanding something.
The mark here is the line or marker from which a competitor starts a race, as is also the case in get off the mark and on your marks.
be ˌquick/ˌslow off the ˈmarkbe quick/slow to do something or understand something: You have to be quick off the mark when you answer a newspaper advertisement for an apartment. ♢ Jenny was rather slow off the mark, and they had to explain the joke to her.
In athletics, your mark is your starting point in a race.