1a period when all lights must be turned out or covered to prevent them being seen by the enemy during an air raid:people found it difficult to travel in the blackout [as modifier]:she peered out through the blackout curtains
(usually blackouts) British dark curtains put up in windows to cover lights during an air raid.
a failure of an electrical power supply:due to a power blackout their hotel was in total darkness
a moment in the theatre when the lights on stage are suddenly dimmed.
a suppression of information, especially one imposed on the media by government:there is a total information blackout on minority interests
2a temporary loss of consciousness:she was suffering from blackouts