variable resistor; potentiometer
Wasei-eigo term used in electronics; refers to a variable resistor or potentiometer. Not standard English.
wasei-eigo (Japanese-coined English), from vari-ohm
In this circuit, we use a variable resistor to adjust the voltage.
Wasei-eigo from English 'vari-ohm', combining 'variable' and 'ohm'. The exact origin is uncertain, but it likely arose in Japanese electronics terminology.