refine has 7 distinct synonyms spread across 3 of its 6 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.
make more complex, intricate, or richer
“refine a design or pattern”
treat or prepare so as to put in a usable condition
“refine paper stock”
attenuate or reduce in vigor, strength, or intensity by polishing or purifying
“many valuable nutrients are refined out of the foods in our modern diet”
make more precise or increase the discriminatory powers of
“refine a method of analysis”
Synonyms, antonyms and the broader and narrower relations for refine come from Princeton University’s WordNet. Full sources and licences.