crys ‧ tal /ˈkrɪstl/ BrE AmE noun
[ Date: 1000-1100 ; Language: Old French ; Origin: cristal , from Latin crystallum , from Greek krystallos 'ice, crystal' ]
1 . [uncountable] very high quality clear glass:
a set of six crystal glasses
2 . [countable] a small regular-shaped piece of a substance, formed naturally when this substance becomes solid:
ice crystals
copper sulphate crystals
3 . [uncountable and countable] rock that is clear, or a piece of this
4 . [countable] American English the clear cover on a clock or watch