verb (v)

• improve or perfect by pruning or polishing(verb.change)

  Synonym:
  down, polish, refine
  

  source: wordnet30
• adjust finely(verb.change)

  Example:
  Fine-tune the engine.
  

  Synonym:
  tweak
  

  source: wordnet30
• make fine adjustments or divide into marked intervals for optimal measuring(verb.change)

  Synonym:
  calibrate, graduate
  

  source: wordnet30