siding vs railroad siding

siding and railroad siding both are nouns.

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

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

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

Other synonyms of siding include sidetrack, turnout.

siding (noun)	railroad 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