( pl PXs ) ( in full post exchange ) n [ usu sing ] ( AmE )
a general shop on a US army base for members of the armed forces and their families. It sells a wide range of goods, such as clothes, gifts, food, etc. Prices are cheaper than in regular shops because there are no taxes and the PX does not make a profit. Such a shop on a US Air Force base is called a BX (base exchange) and on a US Navy base or ship it is called a commissary .