Source : Webster's Revised Unabridged Dictionary (1913)

Opaqueness \O*paque"ness\, n.
   The state or quality of being impervious to light; opacity.
   --Dr. H. More.

Source : WordNet®

opaqueness
     n 1: incomprehensibility resulting from obscurity of meaning
          [syn: {opacity}]
     2: the quality of being opaque to a degree; the degree to which
        something reduces the passage of light [syn: {opacity}]
        [ant: {clearness}]