'major axis' definitions:

Definition of 'major axis'

(from WordNet)
noun
The longest axis of an ellipse or ellipsoid; passes through the two foci

Definition of 'major axis'

From: GCIDE
  • major axis \major axis\ n. (Geom.), The greater axis of a geometrical figure. Especially: the longest axis of an ellipse or ellipsoid, which passes through the two foci. See Focus, n., 2. [WordNet 1.5 +PJC]