abacus
noun [ C ] uk/ˈæb.ə.kəs/ us/ˈæb.ə.kəs/
(COUNTING TOOL)
算盘
a square or rectangular frame holding an arrangement of small balls on metal rods or wires, used for counting or for doing calculations
(IN BUILDING)
architecture specialized（圆柱）顶板
a flat slab (= piece of stone, etc.) at the top of a column