refine

Short definition from Wiktionary

Verb

1. 1
   To purify; reduce to a fine, unmixed, or pure state; to free from impurities.
2. 2
   To become pure; to be cleared of impure matter.
3. 3
   To purify of coarseness, vulgarity, inelegance, etc.; to polish.
4. 4
   To improve in accuracy, delicacy, or excellence.
5. 5
   To make nice or subtle.