graveyard watch vs night watch

graveyard watch and night watch both are nouns.

Word	Noun	Adjective	Verb	Adverb
graveyard watch	Yes	No	No	No
night watch	Yes	No	No	No

As nouns, graveyard watch and night watch are synonyms defined as:

graveyard watch and night watch: a watch during the night (as from midnight to 8 a.m.)

Other synonyms of graveyard watch include middle watch, midwatch.

graveyard watch (noun)	night watch (noun)
a watch during the night (as from midnight to 8 a.m.)	a watch during the night (as from midnight to 8 a.m.)