pumice
1. pum.ice \'p*m-*s\ \pyu:-'mish-*s, .p*-\ n [ME pomis, fr. MF, fr. L pumic-, pumex - more at FOAM] : a volcanic glass full of cavities and very light used esp. in powder for m for smoothing and polishing - pu.mi.ceous aj 2. pumice vt : to clean, smooth, or treat with pumice