(a.) Rubbed smooth.

abate abrade abrase absorb assimilate atomize bark bate be eaten away bleed white break up burn up chafe come apart consume consume away corrode crack up crumble crumble into dust decay decline decompose decrease deliquesce deplete depreciate die away digest diminish disintegrate disjoin disorganize dissipate dissolve dive drain drain of resources dribble away drop drop off dwindle eat eat up ebb erase erode exhaust expend fall fall away fall off fall to pieces file finish finish off fission fray frazzle fret gall gnaw gnaw away gobble gobble up grate graze grind impoverish ingest languish lessen let up melt away molder plummet plunge rasp raze rub away rub off rub out run low sag scour scrape scrub scuff shrink sink skin spend split squander subside suck dry swallow swallow up tail off tatter use up wane waste waste away wear wear away wear down wear off wear out wear ragged weather