railroad has 7 distinct synonyms spread across 3 of its 5 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
supply with railroad lines
“railroad the West”
line that is the commercial organization responsible for operating a system of transportation for trains that pull passengers or freight
a line of track providing a runway for wheels
“he walked along the railroad track”
Synonyms, antonyms and the broader and narrower relations for railroad come from Princeton University’s WordNet. Full sources and licences.