Pumice

pum′is, or pū′mis, n. a hard, light, spongy substance, formed of lava, from which gas or steam has escaped while hardening.— v.t. to polish or rub with pumice-stone—also Pū′micāte .— adjs. Pumi′ceo us , Pum′iciform , of or like pumice.— ns. Pum′ice-stone (same as Pumice ); Pū′my ( Spens. ), a pebble, stone. [A.S. pumic- ( -stán ), pumice (-stone)—L. pumex , pumicis , for spumex — spuma , foam— spuĕre . Cf. Spume , and Pounce , a fine powder.]