Middle English pomis, from Anglo-French pomice, from Latin pumic-, pumex — more at foam
First Known Use: 15th century
Medical Definition of PUMICE
: a volcanic glass full of cavities and very light in weight used especially in powder form for smoothing and polishing
Very porous, frothlike volcanic glass that has long been used as an abrasive in cleaning, polishing, and scouring compounds. It is also used in precast masonry units, poured concrete, insulation and acoustic tile, and plaster. Pumice is igneous rock that cooled so rapidly there was no time for it to crystallize. When it solidified, the vapours dissolved in it were suddenly released, and the whole mass swelled up into a froth that immediately consolidated. Any type of lava may become pumiceous under favourable conditions.