crupper
noun
- a padded leather strap passed around the base of a horse's tail and attached to the saddle or harness to keep it from moving forward
- the croup of a horse
- Informal the buttocks
See crupper in American Heritage Dictionary 4
crup·per
noun- A leather strap looped under a horse's tail and attached to a harness or saddle to keep it from slipping forward.
- The rump of a horse; the croup.
Origin: Middle English crouper, from Old French cropiere, from croupe, rump; see croup 2.