Loss of consciousness due to the interruption of breathing and consequent anoxia.
Loss of consciousness due to the body's inability to deliver oxygen to its tissues, either by the breathing of air lacking oxygen or by the inability of the blood to carry oxygen.
A temporary loss of consciousness.
The blocking out of as much light as possible.
A large-scale power failure, and resulting loss of electricity to consumers.
A temporary loss of memory.
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.
An instance of censorship, especially a temporary one.