A HACK is a horse used for riding, rather than for sport. In the show ring, a hack is an elegant animal, finely built and the picture of sophistication. The Julip Hack does not fir that picture very well !! He's quite a plain horse, poor thing.
Julip made many pony models of breeds and generic types - like the next on the list, the HANDY HUNTER. Handy hunter is a class at gymkhanas where ponies and riders do a series of tasks to prove how versatile they are.