A hypothetical construct of economic theory representing the place all potential buyers and sellers of all goods and services come together, express their desires and offer their wares, through bargaining establish a price structure and production schedule, and complete their transactions. In standard usage it refers to all locations where economic transactions occur treated as a single whole. 

Source: Schwarz, Charles F.; Thor, Edward C.; Elsner, Gary H. 1976. Wildland planning glossary. Gen. Tech. Rep. PSW-13. Berkeley, Calif.: U.S. Department of Agriculture, Forest Service, Pacific Southwest Forest and Range Experiment Station via NALT