0 to make a substance pure by removing other substances from it -- raffinare
1 to improve an idea, method, system, etc. by making small changes -- migliorare, perfezionare
2 to make (a substance eg sugar) pure by taking out dirt, waste substances etc -- raffinare
Oil is refined before it is used.
3 to improve -- migliorare
We have refined our techniques considerably since the work began.