An algebraic surface of degree 9.
Enneper's minimal surface is an example of a nonic surface.
Nonic Surface
See also
Algebraic SurfaceExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Nonic Surface." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/NonicSurface.html