Barbecue (also barbeque, BBQ and barbie) is a cooking method and apparatus. In the United States, to grill is to cook meat relatively quickly using the direct heat imparted by a charcoal or propane fire, while barbecue is a much slower method utilizing the indirect heat imparted by the smoke of a wood-fueled fire, often requiring an extended period of several hours. While there is a vast degree of variation and overlap in terminology and method surrounding this form of cooking, the generally accepted difference between barbecue and grilling is in the cooking time and type of heat used: grilling is generally done "hot and fast" over direct heat from low-smoke fuels (with the flame contacting the meat itself), while barbecuing is usually done "low and slow" over indirect heat from high-smoke fuels (with the flame not contacting the meat directly). The term as a noun can refer to the meat or to the cooking apparatus itself (the "barbecue grill" or simply "barbecue"). The term 'barbecued' is used as an adjective and refers to foods cooked by this method. The term is also used as a verb for the act of cooking food in this manner. Barbecuing is usually done in an outdoor environment by smoking the meat over wood or charcoal. Restaurant barbecue may be cooked in large brick or metal ovens specifically designed for that purpose. Although barbecue has become largely identified with Southern cooking in the United States, barbecuing has numerous regional variations in many parts of the world.