In deep typography circles, 'parametric fonts' means typefaces where their attributes are isolated and can be controlled as parameters.
That can be done with OpenType Variable Fonts (eg Decovar and Amstelvar) but is not commonly done with them (eg OTvar fonts with just Weight and Width axes)
Its more common that parametric fonts are made with 'generative font' formats, like metafont and www.Prototypo.io, where there is a turing complete programming language that controls and generates the letter shapes.
That can be done with OpenType Variable Fonts (eg Decovar and Amstelvar) but is not commonly done with them (eg OTvar fonts with just Weight and Width axes)
Its more common that parametric fonts are made with 'generative font' formats, like metafont and www.Prototypo.io, where there is a turing complete programming language that controls and generates the letter shapes.