refiner

transitive verb refined, refining

1. to make fine or pure; free from impurities, dross, alloy, sediment, etc.; purify; clarify
2. to free from imperfection, coarseness, crudeness, etc.; make more elegant or cultivated; impart polish to
3. to make more subtle or precise

Origin: re- + fine, v., based on Fr raffiner, to purify

intransitive verb

1. to become fine or pure; become free from impurities, etc.
2. to become more polished or elegant
3. to use subtleties and fine distinctions in thinking or speaking