lights-out

n.

1.

a signal to turn the lights out.

Thesaurus

Noun	1.	lights-out - a prescribed bedtime night, nighttime, dark - the time after sunset and before sunrise while it is dark outside bedtime - the time you go to bed
	2.	lights-out - (military) signal to turn the lights out taps bugle call - a signal broadcast by the sound of a bugle armed forces, armed services, military, military machine, war machine - the military forces of a nation; "their military is the largest in the region"; "the military machine is the same one we faced in 1991 but now it is weaker"