A point 
on a regular surface 
is said to be parabolic if the Gaussian
curvature 
but 
(where 
is the shape operator), or equivalently, exactly
one of the principal curvatures 
equals 0.
Parabolic Point
See also
Anticlastic, Elliptic Point, Gaussian Curvature, Hyperbolic Point, Planar Point, SynclasticExplore with Wolfram|Alpha
References
Gray, A. Modern Differential Geometry of Curves and Surfaces with Mathematica, 2nd ed. Boca Raton, FL: CRC Press, p. 375, 1997.Referenced on Wolfram|Alpha
Parabolic PointCite this as:
Weisstein, Eric W. "Parabolic Point." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/ParabolicPoint.html