lights-out vs taps

lights-out and taps both are nouns.

Word	Noun	Adjective	Verb	Adverb
lights-out	Yes	No	No	No
taps	Yes	No	No	No

As nouns, lights-out and taps are synonyms defined as:

lights-out (noun)	taps (noun)
(military) signal to turn the lights out	(military) signal to turn the lights out
a prescribed bedtime