the extinguishing or concealment of all visible lights in a city, military post, etc., usually as a precaution against air raids.
a period during a massive power failure when the lack of electricity for illumination results in utter darkness except from emergency sources, as candles.
the extinguishing of all stage lights, as in closing a vaudeville skit or separating the scenes of a play.
Also called blackout skit. a skit ending in a blackout.
temporary loss of consciousness or vision: She suffered a blackout from the blow on the head.
a period of total memory loss, as one induced by an accident or prolonged alcoholic drinking: The patient cannot account for the bizarre things he did during his blackout.
a brief, passing lapse of memory: An actor may have an occasional blackout and forget a line or two.
complete stoppage of a communications medium, as by a strike, catastrophe, electrical storm, etc.: a newspaper blackout; a radio blackout.
a stoppage, suppression, or obliteration: a news blackout.
a period during which a special sales offer, fare rate, or other bargain is not available: The airline's discount on fares does not apply during the Christmas week blackout.
Radio and Television. a prohibition that is imposed on the broadcasting of an event and has the purpose of encouraging or ensuring ticket sales.

1910–15; noun use of verb phrase black out

blackout, brownout. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
blackout (ˈblækaʊt)
1.  the extinguishing or hiding of all artificial light, esp in a city visible to an enemy attack from the air
2.  a momentary loss of consciousness, vision, or memory
3.  a temporary electrical power failure or cut
4.  electronics a temporary loss of sensitivity in a valve following a short strong pulse
5.  a temporary loss of radio communications between a spacecraft and earth, esp on re-entry into the earth's atmosphere
6.  the suspension of radio or television broadcasting, as by a strike or for political reasons
7.  (tr) to obliterate or extinguish (lights)
8.  (tr) to create a blackout in (a city etc)
9.  (intr) to lose vision, consciousness, or memory temporarily
10.  (tr, adverb) to stop (news, a television programme) from being released or broadcast

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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Word Origin & History

1913 in the theatrical sense of a darkened stage, from black + out. Figurative sense of "loss of memory" is 1934; as a dousing of lights as an air raid precaution, it is recorded from 1935.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

blackout black·out (blāk'out')

  1. Temporary loss of consciousness due to decreased blood flow to the brain.

  2. Temporary loss of memory.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Cultural Dictionary

blackout definition

The complete loss of electrical power in a particular area. Blackouts can result from a natural disaster, a manmade catastrophe, or simply from an excess of energy demand over supply. (Compare brownout.)

Note: Rolling blackouts to match supply and demand have become increasingly common in the United States.
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Example sentences
Trip specifics are subject to availability and blackout dates.
Without the blackout there will be no story, so no awareness.
The region was in an accustomed power blackout that night.
The blackout caused shock waves because it had not been done before by a
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