rubber has 18 distinct synonyms spread across 7 of its 8 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 elastic material obtained from the latex sap of trees (especially trees of the genera Hevea and Ficus) that can be vulcanized and finished into a variety of products
any of various synthetic elastic materials whose properties resemble natural rubber
a contest consisting of a series of successive matches between the same sides
“he won three out of five games to take the rubber”
an eraser made of rubber (or of a synthetic material with properties similar to rubber); commonly mounted at one end of a pencil
contraceptive device consisting of a sheath of thin rubber or latex that is worn over the penis during intercourse
Synonyms, antonyms and the broader and narrower relations for rubber come from Princeton University’s WordNet. Full sources and licences.