mill has 13 distinct synonyms spread across 6 of its 9 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 plant consisting of one or more buildings with facilities for manufacturing
Scottish philosopher who expounded Bentham's utilitarianism; father of John Stuart Mill (1773-1836)
English philosopher and economist remembered for his interpretations of empiricism and utilitarianism (1806-1873)
machinery that processes materials by grinding or crushing
Synonyms, antonyms and the broader and narrower relations for mill come from Princeton University’s WordNet. Full sources and licences.