pumice

Từ điển WordNet v3.1 - WordNet Dictionary

I - noun

a light glass formed on the surface of some lavas;
used as an abrasive
• Syn:
pumice stone
• Hypernyms:
rock, stone

II - verb

rub with pumice, in order to clean or to smoothen
• Hypernyms:
rub
• Verb Frames:
- Somebody ----s something