major axis definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
Geom. the longer axis of an ellipse, that passes through both focus points
major axis definition by American Heritage Dictionary
The longer of the two lines about which an ellipse is symmetrical; the axis that passes through both focuses of an ellipse.