A surface on which the Gaussian curvature 
is everywhere positive.
When 
is everywhere negative,
a surface is called anticlastic. A point at which
the Gaussian curvature is positive
is called an elliptic point.
Synclastic
See also
Anticlastic, Elliptic Point, Gaussian Quadrature, Hyperbolic Point, Parabolic Point, Planar PointExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Synclastic." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Synclastic.html