A curve in one plane traced by a point moving under the influence of two independent harmonic motions. In the common case the harmonic motions are simple, perpendicular to each other, and have a simple frequency ratio. They can be displayed by applying sinusoidal alternating potentials to the X- and Y-inputs of a cathode-ray oscilloscope. they are named after the French mathematician Jules Lissajous (1822–80).

https://nationalmaglab.org/education/magnet-academy/watch-play/interactive/lissajous-figures-on-an-oscilloscope An interactive simulation of an oscilloscope producing Lissajous figures from the University of Florida