I’d say it has a very loose meaning and can cover any shape/aspect whose overall defining characteristic is curved; either 2D or 3D.
Ovals and circles would be round. Same with Spheres and 3D shapes that have a circular or ovoid cross-section (think a football or a cylinder).
Also, I would describe something like the Epcot Center round, even though it’s comprised of thousands of faced angles/triangular polygons.