Fr: Turkish gown.
Just to make things difficult for the likes of us, there are two different gowns of that name. The earlier robe à la turque was a variation of the robe à la polonaise.
The later robe à la turque came into being around 1790 or shortly thereafter. It had a fitted back (like the anglaise), a considerable train, the waist slightly higher than before, and narrow sleeves the length of T-shirt sleeves.
Late in 1794 or early in 1795, a varitation of the turque came into existence that was called robe à la polonaise but has nothing to do with the earlier polonaise. This late polonaise differs from the robe à la turque mainly by having wrist-legth sleeves - the sleeves of the turque were only 1/3 length. Apart from that, it's hard to say what exactly the difference was.