railroad siding vs siding

railroad siding and siding both are nouns.

Word	Noun	Adjective	Verb	Adverb
railroad siding	Yes	No	No	No
siding	Yes	No	No	No

As nouns, railroad siding and siding are synonyms defined as:

railroad siding and siding: a short stretch of railroad track used to store rolling stock or enable trains on the same line to pass

Other synonyms of railroad siding include sidetrack, turnout.

railroad siding (noun)	siding (noun)
a short stretch of railroad track used to store rolling stock or enable trains on the same line to pass	a short stretch of railroad track used to store rolling stock or enable trains on the same line to pass
	material applied to the outside of a building to make it weatherproof