Rump Roast
The rump is derived from the round, a cut in the back of the cow. This cut, as a hard-working group of muscles used for movement, can be extremely difficult if not properly prepared. A rump roast is also quite lean, so drying the cut-out is a risk if not properly cooked. Because of its toughness, leanness, and large size, the rump is a relatively inexpensive cut of beef.
Rump roast is ideal for your slow cooker because of its lean meat and firm texture. Low heat for an extended period of time will break down the connective tissue and collagen within the meat, making it tender. Marinades and the various liquids in which the roast can be cooked reduce the risk of the rump drying out and add flavor, which may compensate for the lack of fat.