Definition of diamond noun from the Oxford Advanced Learner's Dictionary

Oxford3000

diamond

noun
ˈdaɪəmənd
 
; ˈdaɪəmənd
 
 
1 [uncountable, countable] a clear precious stone of pure carbon, the hardest substance known.Diamonds are used in jewellery and also in industry, especially for cutting glassa ring with a diamond in ita diamond ring/necklaceShe was wearing her diamonds (= jewellery with diamonds in it).The lights shone like diamonds. see also rough diamond2 [countable] a shape with four straight sides of equal length and with angles that are not right angles3 diamonds [plural, uncountable] one of the four suits (= sets) in a pack/deck of cards. The cards are marked with red diamond shapesthe ten of diamondsDiamonds are/is trumps.4 [countable] a card of this suitYou must play a diamond if you have one.5 [countable] (in baseball) the space inside the lines that connect the four bases; also used to mean the whole baseball field