The Collaborative International Dictionary
Goose-rumped \Goose"-rumped`\, a. (Zo["o]l.) Having the tail set low and buttocks that fall away sharply from the croup; -- said of certain horses.
Wiktionary
a. (context of a horse or donkey etc English) having a steep, sloping croup, a narrow rump, and a low set to the tail
Usage examples of "goose-rumped".
Weaver had gone with the ranch, just a goose-rumped Mexican grade horse worth a couple hundred bucks, tops.
As for Banningham's cub, riding that goose-rumped gray of his up the stairs at Brent Lodge, and your Courtenay hunting the squirrel on the Harrogate road—but mum for that!
A steer bawled and fell on its chest in front of a cowboy trying to escape the melee aboard a goose-rumped bay.
He did not note the money-lender on his goose-rumped pony, hastening along to collect the cruel interest.