In cooking, to butterfly something means to cut it down the centre almost, but not completely, through the item. The two halves are then pressed flat to make a butterfly shape.
Butterflying is often done to whole chicken, particularly small Cornish hens, and is easy to accomplish for the home cook. Simply cut out and remove the backbone using kitchen shears or a sharp knife. Then turn the bird breast side up and press down on the breast bone with the back of your hand to flatten the bird. A butterflied bird will cook more quickly than one that is left whole, and can be run under the broiler for a few minutes before serving to crisp the skin. A Cornish hen can be cooked completely under the broiler.
Shrimp can also be butterflied; it works best with larger ones. Cut them through the back as if removing the vein and then flatten; these will cook very quickly.
Butterflied pork chops are also common; the thick but tender boneless chop can be baked or grilled.