Skirt thin sliced bottom round steak is a cut of beef steak from the plate. It is long, flat, and prized for its flavor rather than tenderness. It is not to be confused with hanger steak, a generally similar adjacent cut also from the plate.
Though it is from a different part of the animal, its general characteristics and uses cause it to be confused with both flank steak, taken from the flank behind the plate and the flap meat from the bottom sirloin behind the flank and above the rear quarter. Both the inside and outside skirt steak are the trimmed, boneless portion of the diaphragm muscle attached to the 6th through 12th ribs on the underside of the short plate. This steak is covered in a tough membrane that may be removed before cooking. By keeping the membrane it will be more tender but would require the eater to remove it which is why many remove it prior to cooking.
The inside skirt steak is often confused with the flank steak, which is the tail of the porter house and T-bone steaks of the short loin found on the flank, and hanger steak. The name “skirt steak” for the butcher’s cut of beef diaphragm has been in use since at least the 19th century. The cut is defined as extending to the 10th rib in the early 20th century. Skirt steak is the cut of choice for making fajitas, arrachera, Chinese stir-fry, churrasco, and in Cornish pasties. To minimize toughness and add flavor, skirt steaks are often marinated before grilling, pan-seared or grilled very quickly, or cooked very slowly, typically braised. They are typically sliced against the grain before serving to maximize tenderness.