Skirt steak is a cut of beef steak from the plate. It is long, flat, and prized for its flavor rather than tenderness. Both the inside and outside skirt steak are the trimmed, boneless portion of the diaphragm muscle. This steak is covered in a tough membrane that should be removed before cooking. Skirt steak is the cut of choice for making fajitas, Mexican arrachera, Cornish pasties, Chinese stir-fry, churrasco, and Bolognese sauce.A deep, rich, beefy flavor. When slicing, cut across the grain.