pumice stone
noun [ C ] uk/ˈpʌm.ɪs ˌstəʊn/ us/ˈpʌm.ɪs ˌstoʊn/
浮石，轻石（用来摩擦物体使其光滑）
a piece of pumice used for rubbing things to make them smooth
You can use a pumice stone in the bath to remove dry skin from your feet. 你洗澡时可以用浮石去除脚上干燥的死皮。