1a precious stone consisting of a clear and colourless crystalline form of pure carbon, the hardest naturally occurring substance: [as modifier]:a diamond ring
a tool with a small diamond for cutting glass.
(a diamond) British informal an excellent or very special person or thing:Fred’s a diamond
2 [often as modifier] a figure with four straight sides of equal length forming two opposite acute angles and two opposite obtuse angles; a rhombus:a sweater with a pale-blue diamond pattern
(diamonds) one of the four suits in a conventional pack of playing cards, denoted by a red diamond.
a card of the suit of diamonds:she led a losing diamond
3the area delimited by the four bases of a baseball field, forming a square shape.
a baseball field.
4 [usually as modifier] a railway crossing in which two tracks cross over each other at an acute angle:diamond crossings
diamond cut diamond
used to describe a situation in which a sharp-witted person meets their match.
