1. (

• polish ,
• refine ,
• fine-tune ,
• down

) improve or perfect by pruning or polishing; "refine one's style of writing" ;

2. (

• fine-tune ,
• tweak

) adjust finely; "fine-tune the engine" ;

3. (

• calibrate ,
• graduate ,
• fine-tune ,

) make fine adjustments or divide into marked intervals for optimal measuring; "calibrate an instrument"; "graduate a cylinder" ;