diamond

Concise Oxford English Dictionary © 2008 Oxford University Press:
diamond/ˈdʌɪəmənd/

▶noun

• 1 a precious stone consisting of a clear and colourless crystalline form of pure carbon, the hardest naturally occurring substance.

• 2 a figure with four straight sides of equal length forming two opposite acute angles and two opposite obtuse angles; a rhombus.

• 3 (diamonds) one of the four suits in a conventional pack of playing cards, denoted by a red figure of such a shape.

  ■ a card of this suit.

• 4 a baseball field.

• 5 a railway crossing in which two tracks cross over each other at an acute angle.

– phrases
diamond in the rough North American term for rough diamond.

– derivatives
diamondiferous /-ˈdɪf(ə)rəs/ adjective.

– origin ME: from OFr. diamant, from med. L. diamas, diamant-, var. of L. adamans (see adamant).