The Collaborative International Dictionary of English v.0.48:

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]

The Collaborative International Dictionary of English v.0.48:

Pumice stone \Pum"ice stone`\
   Same as Pumice.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pumice stone
    n 1: a light glass formed on the surface of some lavas; used as
         an abrasive [syn: pumice, pumice stone]

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "pumice stone":
   abstergent, cathartic, cleaner, cleaning agent, cleaning solvent,
   cleanser, cleansing cream, cold cream, cream, dentifrice, depurant,
   detergent, diuretic, emetic, enema, holystone, lotion, mouthwash,
   nauseant, purgative, purge, purifier, rinse, shampoo, soap,
   solvent, synthetic detergent, tooth powder, toothpaste, wash