Crupper

n.	1.	The buttocks or rump of a horse.
	2.	A leather loop, passing under a horse's tail, and buckled to the saddle to keep it from slipping forwards.
v. t.	1.	To fit with a crupper; to place a crupper upon; as, to crupper a horse.

Noun

1.

crupper - a strap from the back of a saddle passing under the horse's tail; prevents saddle from slipping forward

back band, backside, backstrap, bearing rein, behind, bellyband, bit, blinders, blinds, breeching, bridle, butt, buttocks, caparison, cavesson, checkrein, cheekpiece, chinband, cinch, collar, croup, crownband, curb, gag swivel, girth, hackamore, halter, hames, hametugs, harness, haunches, headgear, headstall, hind end, hip straps, jaquima, jerk line, lines, martingale, nates, noseband, pole strap, posterior, rear, rear end, reins, ribbons, rump, saddle, shaft tug, side check, snaffle, surcingle, tack, tackle, trappings, tug, winker braces, yoke