What does "nightfall" mean?

The close of the day; the coming of night.

What is a synonym for "nightfall"?

Common synonyms include: dusk, twilight, cockshut, collapse, crepuscle, crepuscule.

/ˈnaɪt.fɔl/ noun

noun ·Uncommon ·Advanced level

Noun

1
The close of the day; the coming of night. countable, uncountable
"at nightfall"
2
the time of day immediately following sunset wordnet
3
Nocturnal emission. countable, uncountable

"Judging from the look of the sky, we might have a shower before nightfall."

From night + fall. Cf. dewfall.