Origin: 1200-1300 Old French diamant hard metal, diamond, from Greek adamas
1 [countable, uncountable] a clear, very hard valuable stone, used in jewelry and in industry: a diamond necklace2[countable] a shape with four straight sides of equal length that stands on one of its points: Cut the cookie dough into diamonds.3[countable]a)the area in a baseball field that is within the diamond shape formed by the four basesb)the whole playing field used in baseball4a)diamonds one of the four types of cards in a set of playing cards, which has the shape of a red diamond on it: the two of diamondsb)[countable] a card with this shape on it: Play a diamond.5a diamond in the rough someone or something that has the possibility of being good, valuable, or attractive, but needs improvement [Origin: 1200–1300 Old French diamant hard metal, diamond, from Greek adamas]