blackout

1. (Internet) An intentional outage of a website or other online service, typically as a form of protest.Examples: "the 2012 English Wikipedia blackout"; "A group of Redditors, many of whom are moderators, organized a temporary boycott, with participating subreddits going private or restricted for 48 hours starting on Monday. A Twitch stream tracking the blackout claimed that nearly 8,500 subreddits, some with tens of millions of subscribers, had gone dark by Tuesday afternoon."Internetcountableuncountable

2. (historical) The 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.Examples: "In co-operation with the Government departments, the British railway companies prepared their stations, offices, docks, hotels, trains, and other premises for the necessary blackout of lighting that it was realised would be required in a state of emergency, and in the case of the experimental voluntary blackouts which took place in July and August the railway companies concerned co-operated in every way possible."; "During the "blackout", many real cars and lorries had their front wings painted white, in order to avoid accidents."countablehistoricaluncountable

3. (attributive) The blocking out of as much light as possible.Examples: "blackout blinds; blackout curtains"attributivecountableuncountable

4. (slang, criminology, rare) A mass murder committed, usually in an urban area, to eliminate potential witnesses of a previous crime.countablerareslanguncountable