1. The quality or the degree to which something reduces the passage of light: The opaqueness of the dirty windows permitted little light to pass through them and so they were not translucent or they were just clear enough for light to pass through them, but only with difficulty.

Dust storms are common across Arizona during dry and windy conditions, and walls of dust more than a mile high can blanket an area in a matter of seconds, sometimes reducing visibility to zero or complete opaqueness.

2. Incomprehensibility resulting from the obscurity or difficulty of understanding someone or something: The opaqueness of technical jargon found in most scientific dictionaries makes it very difficult for the average user to understand what is being presented.

Why must so many medical lexicons have such opaquenesses in their content?