The Oxford Thesaurus An A-Z Dictionary of Synonyms - opaqueadj.

1) dark, murky, dim, turbid, muddy, cloudy, obscure, obscured, obfuscated, black, impermeable, impenetrable, clouded, non-transparent, untransparent, non-translucent, hazy, blurred, blurry, smoky: Solar eclipses should be viewed directly only through special opaque glass. 2) unclear, vague, indefinite, obscure, unfathomable, unplumbable, baffling, mystifying, ambiguous, equivocal, impenetrable, cryptic, enigmatic, puzzling, perplexing, mysterious, elusive, abstruse, arcane, recondite: Despite years of study, the inscriptions on the tomb have remained opaque to scholars. 3) unintelligent, dense, thick, dull, obtuse, stupid, dull-witted, stolid, thickheaded, dunderheaded, dunderpated, slow, doltish, backward, cloddish: He was too opaque to notice the jeers of his colleagues.