The term 'not metaphysical' can be described as CONCRETE, which is an 8-letter word. CONCRETE is a material composed of fine and coarse aggregate bonded together with a fluid cement that hardens over time. It is most commonly used for construction purposes, such as foundations, walls, and roads. CONCRETE is also used in the production of precast CONCRETE products, such as blocks, pipes, and bricks. It is a durable material that is resistant to weathering and erosion.