The phrase "hay stack" refers to a pile or stack of dried grass called hay, which is typically used as animal feed or bedding on farms. Full definition
Perfect for climbing hay stacks and walking through the pumpkin patch! (mystylepill.com)
Bales of hay stacked up outside Kibbutz Samar. (treehugger.com)
Climbing the tires, playing in the corn, playing on hay stacks, riding a hopper ball in a hay bale ring, riding a pipe swing, and enjoying some lemonade were some of the other things our 4 - year - old enjoyed most on our farm visit too. (bhamfunandfamily.com)