black·out / ˈblakˌout/ • n. 1. a 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 adj.] she peered out through the blackout curtains. ∎ a failure of electrical power supply: due to a power blackout, their hotel was in total darkness.2. a suppression of information, esp. one imposed on the media by government: there is a total information blackout on minority interests. ∎ a period during which a particular activity is prohibited: there are no blackout days during the travel period.3. a temporary loss of consciousness: she was suffering from blackouts.