brakeman vs railroad man

brakeman and railroad man both are nouns.

Word	Noun	Adjective	Verb	Adverb
brakeman	Yes	No	No	No
railroad man	Yes	No	No	No

As nouns, railroad man is a hypernym of brakeman; that is, railroad man is a word with a broader meaning than brakeman:

Other hypernyms of brakeman include railroader, railway man, railwayman, trainman.

brakeman (noun)	railroad man (noun)
a railroad employee responsible for a train's brakes	an employee of a railroad