Could be:think on one's feet
to think and react quickly, especially in a situation where things are happening very fast.
An ability to think on your feet is a definite advantage when you're doing live comedy shows.think on one's feet
Fig. to be able to speak and reason well while (standing and talking) in front of an audience, especially extemporaneously.
She really thinks on her feet well.
I am not able to think on my feet too well before a bunch of people.
Sem um maior contexto eu diria que é a capacidade de pensar e reagir com rapidez frente uma situação ou algo que acontece subitamente
. Essa é a primeira definição acima
Source: The Free Dictionary