Synonyms for opaque

modified

1. Impervious to light

   nontransparent, dim, dusky, darkened, darkling, murky, gloomy, lusterless, smoky, thick, misty, cloudy, clouded, shady, turbid, muddy, dull, blurred, frosty, filmy, foggy, sooty, dirty, dusty, fuliginous, nubilous, nontranslucent, absorbing light, coated over, covered; see also dark 1, hazy 1.

   Antonyms clear*, transparent, translucent.

2. Relatively impervious to understanding

   concealed, enigmatic, perplexing; see obscure 1, vague 2.