Definition of horse litter:
(n) :
Straw or similar litter used for horses' rest or, once mixed with horse urine and excrement, as a waste product or fertilizer.
(n) :
A litter pulled or borne by one horse or borne on poles borne by two or more horses.
(n) :
(uncommon) Synonym of horsecart, particularly in contexts for carrying the injured or deceased in early cart ambulances or hearses.