horsebox

From horse +‎ box.

horsebox (plural horseboxes)

1. (UK) A motor vehicle for transporting horses.
2. A container for transporting horses in, whether by road, rail, or sea.
3. (UK, rail transport, obsolete) A van-type railway vehicle specially built for the carriage of horses.
   • 1960 January, “Motive Power Miscellany: Western Region”, in Trains Illustrated, page 58:

     On October 31 [...] Laira "Grange" No. 6871 passed through Wolverhampton with a Holyhead-Didcot horsebox special.

Unlike US horse trailers, horseboxes are rather small, but there are large horseboxes, coachbuilt on lorry chassis, mainly for carrying racehorses and police horses. Horse trailers may be quite large, transporting a large number of horses.

• “horsebox”, in Lexico, Dictionary.com; Oxford University Press, 2019–2022.