antibiotic has 1 distinct synonym spread across 1 of its 2 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.
a chemical substance derivable from a mold or bacterium that can kill microorganisms and cure bacterial infections
“when antibiotics were first discovered they were called wonder drugs”
1 of the 2 recorded senses carries no synonym, antonym or related term, so it is not shown above. Every sense, with its definition and examples, is on the full entry for antibiotic.
Synonyms, antonyms and the broader and narrower relations for antibiotic come from Princeton University’s WordNet. Full sources and licences.