railroad vs broad gauge

railroad and broad gauge both are nouns.

Word	Noun	Adjective	Verb	Adverb
railroad	Yes	No	Yes	No
broad gauge	Yes	No	No	No

As nouns, broad gauge is a hyponym of railroad; that is, broad gauge is a word with a more specific, narrower meaning than railroad:

railroad: a line of track providing a runway for wheels
broad gauge: a railroad track (or its width) broader than the standard 56.5 inches

Other hyponyms of railroad include gantlet, narrow gauge, railroad siding, sidetrack, siding, turnout, standard gauge, switch.

railroad (noun)	broad gauge (noun)
line that is the commercial organization responsible for operating a system of transportation for trains that pull passengers or freight	a railroad track (or its width) broader than the standard 56.5 inches
a line of track providing a runway for wheels

railroad (verb)	broad gauge (verb)
transport by railroad
supply with railroad lines
compel by coercion, threats, or crude means