1.A large and to some degree orderly pile of hay, grain, straw, or the like, usually of a nearly conical form, but sometimes rectangular or oblong, contracted at the top to a point or ridge, and sometimes covered with thatch. "But corn was housed, and beans were in the stack."
2.Hence: An orderly pile of any type of object, indefinite in quantity; used especially of piles of wood. A stack is usually more orderly than a pile "Against every pillar was a stack of billets above a man's height."
3.Specifically: A pile of wood containing 108 cubic feet. (Eng.)
4.Hence: A large quantity; as, a stack of cash. (Informal)
7.pl. The section of a library containing shelves which hold books less frequently requested.