/ əʊˈpeɪk; NAmE oʊ-/ adjective
1.
( of glass, liquid, etc. ) not clear enough to see through or allow light through :
opaque glass
opaque tights
2.
( of speech or writing ) difficult to understand; not clear
SYN impenetrable :
The jargon in his talk was opaque to me.
OPP transparent
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WORD ORIGIN
late Middle English opake , from Latin opacus darkened. The current spelling (rare before the 19th cent.) has been influenced by the French form.