Rump (noun)

1. The hindquarters of a quadruped animal, such as a horse or a cow.
2. The fleshy part of the body that lies between the hips and the base of the tail in humans and some animals.

Origin:

From middle english 'romp'.

Examples:

1. The rump of the horse was muscular and well-defined.
2. The cow's rump was covered in mud from rolling in the pasture.
3. She massaged her sore rump after sitting for too long.
4. The rump steak was tender and juicy.
5. The rump roast was slow-cooked to perfection.