Same word as opaque:

blurred, cloudy, dark, darkened, dim, dirty, dull, dusky, filmy, foggy, frosty, fuliginous, gloomy, hazy, impenetrable, lusterless, misty, muddied, murky, nontranslucent, nontransparent, nubilous, obfuscated, shady, smoky, sooty, thick, turbid