The line connecting the points of maximum flattening on earth's surface is called the

AXIS.

Axis in geography can be said to be an imaginary line around which an object turns. Usually a round object, can be a planet, asteroid, moon etc.

The points where an axis intersects with an object's surface are the object's North and South Poles.

Rotation about a fixed axis is a special case of rotation. Whereby an object rotates along an imaginary line.