1. A cutoff of electrical power, especially as a result of a shortage, a mechanical failure, or overuse by consumers.
2. The concealment or extinguishment of lights that might be visible to enemy aircraft during an air raid.
3. 1. The sudden extinguishment of all stage lights in a theater to indicate the passage of time or to mark the end of an act or scene.
   2. A short, comic vaudeville skit that ends with lights off.
4. A temporary loss of memory or consciousness.
5. 1. A suppression, as of news, by censorship.
   2. Restriction or prohibition of telecasting a sports event in order to ensure ticket sales.

SYNONYMS   blackout, faint, swoon, syncope. These nouns denote a temporary loss of consciousness: suffers blackouts at high altitudes; fell in a dead faint at the sight of the body; sank to the ground in a swoon; was taken to the clinic in a state of syncope.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.