Definition of "tuner"

A person who tunes a piano or organ.  examples

A device, electronic or mechanical, that helps a person tune a musical instrument by showing the deviation of the played pitch from the desired pitch.  examples

On a musical instrument, a peg or mechanical device that changes the tension, and hence pitch, of a string.  examples

The component of an audio system that receives radio broadcasts.  examples

(archaic) One who sings or makes music.

(entertainment industry, informal) A musical.  examples