lights-out

Short definition from Wiktionary

Noun

1. 1
   The time at night at which artificial lights are to be turned off, a curfew or bedtime.
2. 2
   The prescribed bedtime for persons living in a boarding school or staying in a hospital.
3. 3
   Something hopeless, over; unconsciousness.
4. 4
   Decisive play.
5. 5
   Alternative form of lights-out.
6. 6
   Unconsciousness.

Adjective

1. 1
   Done in the dark because fully automated. Often describes night shift or third shift work.

Verb

1. 1
   third-person singular simple present indicative of light out