Learn English – non-idiomatic word or phrase meaning the same as “on the fly”

phrase-requests

I want to say that someone is quick at thinking on the fly, but need to communicate with non-English speakers. Is there an equivalent non-idiomatic word or phrase?

edit: I want it to imply instantaneous adaptation, "i.e. spur of the moment" but that is idiomatic as well.

Best Answer

extemporaneous - Spoken or done without preparation

That's more for the actions a quick/sharp-witted person might carry out.