Noun
A contrivance for adjusting or regulating the strength of electrical currents, operating usually by the intercalation of resistance which can be varied at will.
Source: Webster's dictionaryElectronic symbols and notation main Two typical schematic diagram symbols are as follows: (a) resistor, (b) rheostat (variable resistor), and (c) potentiometer IEC resistor symbol The notation to state a resistor's value in a circuit diagram varies. Source: Internet
Such a device is called a rheostat and has two terminals. Source: Internet