/ əʊˈpæsəti; NAmE oʊ-/ noun [ U ]
1.
( technical ) the fact of being difficult to see through; the fact of being opaque
2.
( formal ) the fact of being difficult to understand; the fact of being opaque
OPP transparency
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WORD ORIGIN
mid 16th cent.: from French opacité , from Latin opacitas , from opacus darkened.