The tuner in a radio or television set is the part which you adjust to receive different radio or television signals, so that you can watch or listen to the programme that you want.
tuner in British English
(ˈtjuːnə)
noun
1.
a person who tunes instruments, esp pianos
2.
the part of a radio or television receiver for selecting only those signals having a particular frequency
tuner in American English
(ˈtunər; ˈtjunər)
noun
a person or thing that tunes
; specif.,
a.
a person who tunes musical instruments
a piano tuner
b.
the part of a radio or TV receiver that detects signals; esp., a separate unit of a high-fidelity system
Examples of 'tuner' in a sentence
tuner
She had spent the part of it which was most important to her on the move, trotting round beside her father, who was a piano tuner.