loose box

noun2

1. •
   (UK) A separate compartment of a building in which livestock are free to move about; especially a form of stable for horses.

   • Long before you see the lean, handsome heads peering mildly over the half-doors of the loose boxes, you know that East Ilsley's business is training racehorses. — 1980
2. •
   (no longer used) A brougham or other vehicle kept for the use of a dame de compagnie.