Silverside is a term used in the UK, Ireland, Australia and New Zealand for a cut of beef from the hindquarter of cattle, just above the leg cut. It gets its name because of the "silverwall" on the side of the cut; this is a long fibrous "skin" of connective tissue, which has to be removed as it is too tough to eat. The primary muscle is the biceps femoris.
Silverside is boned out from the top along with the topside and thick flank. It is usually prepared as a 2nd class roasting joint. It may also be thinly sliced for minute steak or beef olives, or split in two to produce a salmon-cut.
In Australia, Ireland and New Zealand, silverside is the cut of choice for making corned beef, so much so that the name "silverside" is often used to refer to corned beef rather than any other form of the cut.
In most parts of the U.S., this cut is known as outside or bottom round, as traditionally, a hindquarter is laid on the cutting table with the outside down or to the bottom, as opposed to the inside being on top. In the U.S. it is also known as a rump roast, which means something different in countries using the British beef cut scheme.