'lights-out' definitions:

Definition of 'lights-out'

From: WordNet
noun
A prescribed bedtime
noun
(military) signal to turn the lights out [syn: taps, lights-out]

Definition of 'lights-out'

From: GCIDE
  • lights-out \lights-out\ n. a signal to turn the lights out.
  • Syn: taps. [WordNet 1.5]