/ ˈkrɪstəlaɪn; NAmE / adjective
1.
( technical ) made of or similar to crystals :
crystalline structure / rocks
2.
( formal ) very clear
SYN transparent :
water of crystalline purity
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WORD ORIGIN
Middle English : from Old French cristallin , via Latin from Greek krustallinos , from krustallos ice, crystal.