quick on (one's) feet

1. Able to run very fast. I'm in very good shape, but I've never been quick on my feet. A 10 kilometer run usually takes me about an hour and a half. Did you know that the wildebeest can run as fast as a lion? For such a large animal, it is shockingly quick on its feet.

2. Very nimble and agile. The basketball player is incredibly quick on his feet, able to outmaneuver anyone on the court.

3. With quick, shrewd intelligence. A variant of "quickly on one's feet," usually used after "think." Things can change in an instant in this industry, so you've got to think quick on your feet to be successful. I knew that I had to think quick on my feet if I was going to save the girl's life. A good politician must be able to think quick on their feet when faced with tricky questions from the press.