What is an airfoil called that has zero camber?

An airfoil with zero camber is referred to as symmetrical. In the context of aerodynamics and airfoil design, camber is defined as the curvature of the airfoil's upper and lower surfaces. A symmetrical airfoil has both surfaces shaped identically, meaning that if you were to draw a vertical line through the airfoil's chord line, the airfoil would be evenly balanced above and below this line.

This symmetry results in the airfoil producing the same lift characteristics regardless of the angle of attack, up to a certain point. Essentially, as the angle of attack increases, the symmetrical airfoil experiences the same lift increase as it does when the angle is decreased, until it approaches its critical angle at which stall occurs.

In contrast, unsymmetrical or cambered airfoils have different shapes for the upper and lower surfaces, leading to varied lift properties based on the angle of attack. Flat and round are descriptions of specific geometric shapes and do not inherently define an airfoil with zero camber, which is specifically a characteristic of symmetrical airfoils.