名詞 corundum:

1. very hard mineral used as an abrasive
   同義詞：corundom

co.run.dum

n.（名詞）
An extremely hard mineral, aluminum oxide, Al2O 3, sometimes containing iron, magnesia, or silica, that occurs in gem varieties such as ruby and sapphire and in a common black, brown, or blue form used chiefly in abrasives.
剛玉：一種極為堅(jiān)硬的礦物，氧化鋁，Al2O 3，有時(shí)含鐵、氧化鎂或硅土，存在于各種寶石中，如紅寶石、藍(lán)寶石，并且在磨蝕劑中以普通的黑色、棕色或藍(lán)色形式出現(xiàn)

來源：
Tamil kuruntam
泰米爾語 kuruntam