Skirt steak is a long, flat cut of beef from the diaphragm of the cow, known for its rich, beefy flavor and chewy texture. It is best cooked quickly over high heat, such as grilling or pan-searing, and must be sliced against the grain to avoid toughness. Skirt steak is a versatile cut used in dishes like fajitas, arrachera, and stir-fries.