great circle

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A circle described by the intersection of the surface of a sphere with a plane passing through the center of the sphere.
• noun A segment of such a circle representing the shortest distance between two terrestrial points.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun geometry A circle defined as the intersection of the surface of a sphere and a plane which passes through the centre of the sphere.
• noun A segment of such circle representing the shortest distance between two points on the surface of a sphere.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a circular line on the surface of a sphere formed by intersecting it with a plane passing through the center