burn pit

an area used for the open-air burning of trash and/or brush:

U.S. Military. an often expansive area, at or adjacent to a base of operations, used for the uncontrolled, open-air burning of military waste, including plastics, chemicals, rubber, paint, fuels, munitions, human and medical waste, metals, and electronics: generative of toxic smoke and fumes that have been associated with a number of short- and long-term ailments suffered by exposed military personnel and civilians.