brass has 14 distinct synonyms spread across 5 of its 7 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 copper and zinc
a wind instrument that consists of a brass tube (usually of variable length) that is blown by means of a cup-shaped or funnel-shaped mouthpiece
the persons (or committees or departments etc.) who make up a body for the purpose of administering something
“he claims that the present administration is corrupt”
an ornament or utensil made of brass
the section of a band or orchestra that plays brass instruments
Synonyms, antonyms and the broader and narrower relations for brass come from Princeton University’s WordNet. Full sources and licences.