What do you call the circular thing inside a bathtub? In the picture above, it's submerged in the water. What do you call that thing, right below the faucet?
That is the tub drain overflow plate, though it's actually above the drain, not the faucet. (The opening in this plate leads to a tube that prevents the tub from overflowing by allowing water to run out even if the drain in the bottom of the tub is stopped.)