Definition of "convex"
Curved or bowed outward like the outside of a bowl or sphere or circle.
(Of a set of points) such that for any two points in the set, every point between those two points is also in the set.
(of a real-valued function on the reals) such that the value at any point, is no larger than the interpolated value thereat, based on the values at any two points between which the first point is contained.
Any convex body or surface.