olemus
valgustuse tõkestamine

Wiktionary:
5. (historical) the mandatory blocking of all light emanating from buildings, as well as outdoor and street lighting, as imposed during World War II
6. (attributive) the blocking out of as much light as possible
blackout blinds; blackout curtains

ülevaateid
https://en.wikipedia.org/wiki/Blackout_(wartime)

vt ka
- infosulg
- pimendamine (1)