knob knob /ˈnɑːb/

noun

1. () A circular rounded projection or protuberance  ( boss , knob )
   a circular rounded projection or protuberance
    She turned the knob to adjust the volume of the radio.
   She turned the knob to adjust the volume of the radio.
   
   
2. () A round handle  ( knob )
   a round handle
   
3. An ornament in the shape of a ball on the hilt of a sword or dagger  ( knob , pommel )
   an ornament in the shape of a ball on the hilt of a sword or dagger
   
   
4. Any thickened enlargement  ( knob , node , thickening )
   any thickened enlargement