nightrider vs night rider

nightrider and night rider both are nouns.

Word	Noun	Adjective	Verb	Adverb
nightrider	Yes	No	No	No
night rider	Yes	No	No	No

As nouns, nightrider and night rider are synonyms defined as:

nightrider and night rider: member of a secret mounted band in United States South after the American Civil War; committed acts of intimidation and revenge

nightrider (noun)	night rider (noun)
member of a secret mounted band in United States South after the American Civil War; committed acts of intimidation and revenge	member of a secret mounted band in United States South after the American Civil War; committed acts of intimidation and revenge