: a time when people (such as soldiers, prisoners, or students) are required to turn out the lights and go to bed
Lights-out is at 10 p.m.
They have to be back before lights-out.
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“Lights-out.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/lights-out. Accessed 17 Apr. 2026.
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