olemus
(a) otsene füüsiline läbinähtamatus (physical)

Wiktionary:
1. the state or quality of being opaque, not allowing light to pass through
3. (optics, countable) a measure of relative impenetrability to electromagnetic radiation such as light

(b) ülekantud tähenduses (metaphorical)

Wiktionary:
2.the state or quality of being inaccessible to understanding
The opacity of these decisions is troubling.

näide, ISO/IEC 27033:
sellise teabe kaitstus, mida saab tuletada võrgutoimingute vaatlustest, näiteks VoIP-kõne otspunktide aadressid
= protection of information that might be derived by observing network activities, such as deriving addresses of end-points in a voice-over-Internet-Protocol call
Note. Opacity recognizes the need to protect actions in addition to information.

ülevaateid
https://en.wikipedia.org/wiki/Opacity_(optics)

https://en.wikipedia.org/wiki/Opacity