Definitions
1.NounA temporary loss of consciousness.
2.NounA temporary loss of memory.
3.NounA large-scale power failure, and resulting loss of electricity to consumers.
4.NounAn instance of censorship, especially a temporary one."media blackout"
5.NounAn intentional outage of a website or other online service, typically as a form of protest."the 2012 English Wikipedia blackout"
6.NounThe mandatory blocking of all light emanating from buildings, as well as outdoor and street lighting as a measure against aerial bombing or naval attack, as imposed during, e.g., World War II.
7.NounThe blocking out of as much light as possible."blackout blinds; blackout curtains"
8.NounA mass murder committed, usually in an urban area, to eliminate potential witnesses of a previous crime.
9.VerbAlternative form of black out.