opacity
n. C1 Advanced US //oʊˈpæsəti// UK //ɒpˈæsɪti// opac·i·ty
n. the quality of being hard to see through. You use this to describe things like thick fog, dark glass, or even a secret that is hard to understand.
n. the degree to which a substance or surface prevents the passage of light or other forms of radiation. In a figurative sense, it refers to the quality of being difficult to understand or explain.
The new software update increased the opacity of the background, making the text much easier to read.
The committee's refusal to release the full report created a sense of opacity that led to public suspicion and a loss of trust in the organization.
From opaque + -ity, from French opacité, from Latin opacitas.