Definition
To react or respond to an event or situation with speed or slowness.
反应迅速／迟钝
He was quick off the mark to sell all his stocks when the market started to fall.
当市场开始下跌时，他迅速卖掉了他所有的股票。
She is always quick off the mark, able to seize new business opportunities quickly.
她总是反应迅速，能够迅速抓住新的商业机会。
He was slow off the mark at the start of the race, but he soon caught up.
他在比赛开始时反应迟钝，但很快就赶上了。