I ran into this French phrase in a group of things like "savoir faire" and a few others quite common. But this one I had never heard before, and could not deduce meaning.
I found this on Internet:
L'esprit de l 'escalier" -
the French expression for the moment when you realize what you should have said when confronted with a cutting remark - the clever retort that would have devastated your opponent but only occurs to you after you've left the room and are stomping down the staircase in retreat.
Writers often have this feeling, although some are notoriously good at cracking wise and coming up with the snappy comeback. Parker, Benchley and the other Algonquin wits come to mind, of course. (Pompous young man: "I can't bear fools." Dorothy Parker: "Apparently, your mother could.")
