A stockpile of things is a large quantity of them that have been stored for future use. The two leaders also approved treaties to cut stockpiles of chemical weapons. = stock. a large supply of things that is kept ready for use in the future = store stockpile of. to keep adding to a supply of goods, weapons etc that you are keeping ready to use if you need them in the future
If people stockpile things such as food or weapons, they store large quantities of them for future use. People are stockpiling food for the coming winter. = hoard
Broken ore accumulated in a heap at the mine's surface, pending treatment or shipment to mill, or a stock of metals kept by a government for emergencies