be fast on (one's) feet

1. To be 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. To be 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.