研とぎ石いしMeaningsNoun1. knife sharpener; whetstoneKanji used研refine石stoneComposed of研とぎpolish; grinding; sharpeningNoun石いしstone; rock; pebble; jewel; precious stone; flint (in a lighter); (round) game piece; stone (in go, etc.); disc (in Othello); stone (in the bladder, kidney etc.); …Noun