black out (Noun) — A suspension of radio or tv broadcasting.
black out (Noun) — Darkness resulting from the extinction of lights (as in a city invisible to enemy aircraft).
black out (Noun) — The failure of electric power for a general region.
black out (Noun) — A momentary loss of consciousness.
black out (Noun) — Partial or total loss of memory. ex. "he has a total blackout for events of the evening"
black out (Verb) — Obliterate or extinguish.
black out (Verb) — Darken completely. ex. "The dining room blacked out"
black out (Verb) — Suppress by censorship as for political reasons. ex. "parts of the newspaper article were blacked out"
black out (Verb) — Lose consciousness due to a sudden trauma, for example.