/ ˈpʌmɪs; NAmE / (also ˈpumice stone ) noun
[ U ] a type of grey stone that comes from volcanoes and is very light in weight. It is used in powder form for cleaning and polishing, and in pieces for rubbing on the skin to make it softer.
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WORD ORIGIN
late Middle English : from Old French pomis , from a Latin dialect variant of pumex , pumic- .