railroad engineer vs engineer

railroad engineer and engineer both are nouns.

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

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

Other synonyms of railroad engineer include engine driver, locomotive engineer.

railroad engineer (noun)	engineer (noun)
the operator of a railway locomotive	a person who uses scientific knowledge to solve practical problems
	the operator of a railway locomotive

railroad engineer (verb)	engineer (verb)
	plan and direct (a complex undertaking)
	design as an engineer