the phenomenon of not permitting the passage of electromagnetic radiation
"The heavy storm clouds created such total opacity that not a single ray of sunlight managed to penetrate through to the ground below."
incomprehensibility resulting from obscurity of meaning
"The professor's lecture was filled with such opacity that even the most attentive students left confused by his jargon-heavy explanations."
the quality of being opaque to a degree; the degree to which something reduces the passage of light
"The opacity of the storm clouds made it impossible for even a sliver of sunlight to reach the ground."
The state or quality of being opaque, not allowing light to pass through
"The heavy fog created a complete opacity over the valley, making it impossible to see more than a few feet ahead."