Definition of "opacity" in English

noun

1. (uncountable) The state or quality of being opaque, not allowing light to pass through.

   • We could not see the sandbar due to the opacity of the muddy water.

2. (uncountable) The state or quality of being inaccessible to understanding.

   • The opacity of these decisions is troubling.

3. (optics, countable) A measure of relative impenetrability to electromagnetic radiation such as light.

   • The opacity of a clean glass window is near zero.

4. (countable) An opaque area.