fast on (one's) feet

1. Able to run very fast. I'm in very good shape, but I've never been fast 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 fast on its feet. Because I'm not very fast on my feet, Coach had one of the other guys run for me once I got on base.

2. Very nimble and agile. The basketball player is incredibly fast on his feet, able to outmaneuver anyone on the court. She's a gymnast—of course she's fast on her feet. I'm sure I was fast on my feet as a kid, but those days are long gone now.

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