Is there a French word or, preferably, a suitably obscure French phrase or expression to describe this condition?
And what has prompted this question, I hear you ask. Well, you can blame NickP. I have boasted to him that if I found someone stupid, I wouldn't let on.
I now think that it might be useful to mutter something in French under my breath so as not to give the game away
That is, of course, if I am talking about English-speaking people If I am talking about French people, there isn't the same problem as I know dozens of ways of saying the unspeakable in English
Apprendre une langue, c'est faire un voyage différent chaque jour.
from Fle pour les curieux