Definition of: blackout

(blak′out′) noun
1. A defensive or precautionary measure against aerial attack, consisting of the extinguishment or screening of all lights visible from the air.
2. Physiol. The partial or complete loss of vision and sometimes of consciousness, experienced by airplane pilots during rapid changes in velocity.
3. In theatrics, a fade-out or cut-out, as of part of a scene, eliminating it from view.
4. An official ban on the publication of news in war time, imposed for security reasons.