I do not know what it means

But if you look for "Grande armée" in Napoleon correspondance in 1814 volume (XXVII), you will see that it appears only a few times, and sometime referring to the allies armies, specially Schwarzenberg'.

It is more used just Armée, in oposition to other french armies, like L'Armée d'Espagne or L'Armée du Lyon

In a modern reference it is called Armée in 1814 Tranié books.

The "Grande armée" was not anymore in size nor in quality.