1. (a.) Impervious to the rays of light; not transparent; as, an opaque substance\.

2. (a.) Obscure; not clear; unintelligible.

3. (n.) That which is opaque; opacity.

Boeotian abstruse adiaphanous ambiguous amorphous amphibological arcane asinine backward baffling becloud beef-brained beef-witted black blind blockish blurred blurry bovine chumpish clear as mud cloddish cloud clouded cloudy cowish crass cryptic dark darken dense dim doltish dull dull-witted dullard dumb duncical duncish dunderheaded elusive enigmatic equivocal fat foggy fuzzy gross grumly hazy impenetrable impermeable impervious to light indefinite indeterminate indistinct ineducable intransparent klutzy lumpish misty muddy murky mysterious mystifying nebulous nubilous oafish obfuscated obscure obscured obtuse perplexing puzzling recondite roiled roily shadowy shapeless slow smoky sottish stolid stupid tenebrous thick thickheaded transcendent turbid uncertain unclear unfathomable unintelligent unintelligible unplain unteachable vague wrongheaded