How is it called when one ellipse is "more elliptical" than another one?

Question

Assume you have two ellipses, $A$ and $B$. Now $A$ looks "flatter" than $B$ because its ratio $\frac{\text{major axis}}{\text{minor axis}}$ is bigger. This means it "looks less" than a circle. How is that called? More elliptical?

(I am looking for a description for my bachelor's thesis.)

Source: https://en.wikipedia.org/wiki/File:Elps-slr.svg

Answer 1

Eccentricity is what you're looking for: http://en.wikipedia.org/wiki/Eccentricity_(mathematics)

Answer 2

Eccentricity would be best used to compare the relative "obesity" of ellipses.

Although, Ellipticity (aka Flattening) may also be a good measure of the elliptical nature of ellipses.