Words & Stuff

I’m curious—if I describe a person (or fictional character) as being on the back foot, what would you take from that? Is it a currently standard US-English idiom, or if not, an easily understood metaphor?

This came up in conversation recently, when I happened to say that in the most recent episode of Doctor Who, the Doctor was more reacting to things than moving the plot forward herself, and I said that perhaps that’s a function of the first part of a two-parter, that she would naturally be on the back foot. My conversational partner had not heard the term before, but didn’t have any difficulty understanding what was meant by it. But then, this particular conversational partner has put up with me and my non-standard idioms for decades, now.

Thanks,
-Ed.