'Pumice' definitions:

Definition of 'pumice'

From: WordNet
noun
A light glass formed on the surface of some lavas; used as an abrasive [syn: pumice, pumice stone]
verb
Rub with pumice, in order to clean or to smoothen

Definition of 'Pumice'

From: GCIDE
  • Pumice \Pum"ice\, n. [L. pumex, pumicis, prob. akin to spuma foam: cf. AS. pumic-st[=a]n. Cf. Pounce a powder, Spume.] (Min.) A very light porous volcanic scoria, usually of a gray color, the pores of which are capillary and parallel, giving it a fibrous structure. It is supposed to be produced by the disengagement of watery vapor without liquid or plastic lava. It is much used, esp. in the form of powder, for smoothing and polishing. Called also pumice stone. [1913 Webster]