Anticlastic

When the Gaussian Curvature $K$ is everywhere Negative, a Surface is called anticlastic and is saddle-shaped. A Surface on which $K$ is everywhere Positive is called Synclastic. A point at which the Gaussian Curvature is Negative is called a Hyperbolic Point.

See also Elliptic Point, Gaussian Quadrature, Hyperbolic Point, Parabolic Point, Planar Point, Synclastic