curved surface
General term for any surface that is not flat, used in mathematics, engineering, and everyday description.
The curved surface design of this table is beautiful.
We learned equations for curved surfaces in math class.
hyperboloid
hypersurface
quadric surface
spline surface
Compound of 曲 (curved) and 面 (surface). The reading is on'yomi, as expected for a Sino-Japanese technical term.