/ ˈblækaʊt; NAmE / noun
1.
a period when there is no light as a result of an electrical power failure
2.
a situation when the government or the police will not allow any news or information on a particular subject to be given to the public
3.
( especially BrE ) a period of time during a war when all lights must be put out or covered at night, so that they cannot be seen by an enemy attacking by air
4.
[ usually pl. ] ( BrE ) a covering for windows that stops light being seen from outside, or light from outside from coming into a room
5.
a temporary loss of consciousness , sight or memory :
She had a blackout and couldn't remember anything about the accident.