steel has 4 distinct synonyms spread across 2 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.
an alloy of iron with small amounts of carbon; widely used in construction; mechanical properties can be varied over a wide range
Synonyms, antonyms and the broader and narrower relations for steel come from Princeton University’s WordNet. Full sources and licences.
a cutting or thrusting weapon that has a long metal blade and a hilt with a hand guard
knife sharpener consisting of a ridged steel rod