Another expression for an ellipsoid whose major axis is long

I'm writing a scientific journal.

I'm looking for another expression (or other expressions) for an ellipsoid whose major axis is long (or very long).

(By 'long ellipsoid' what I precisely mean is an ellipsoid whose major axis is much longer than other axes.)

I think 'long ellipsoid' doesn't really sound academical though one can understand it.

Solution 1:

The mathematical term for an extremely oblong ellipsoid or ellipse is “highly eccentric” and an only-slightly-less-technical term is “elongated.” Both terms are used in the Abstract for “Modeling sets of unordered points using highly eccentric ellipses”:

The points are modeled by highly eccentric ellipses, and line segments are extracted by the major axes of these elongated ellipses.

Note: Strictly speaking, the term eccentric applies to ellipses, the two-dimensional cross sections of ellipsoids, which are three dimensional. Even a highly enlongated ellipsoid can have a perfectly circular cross section in some direction, but no mathematician will misunderstand or object to the phrase highly eccentric ellipsoid.

Solution 2:

If both minor axes are of equal length, then the precise term you're looking for the overall character of the shape is prolate spheroid (Wikipedia). From M-W.com:

prolate: elongated in the direction of a line joining the poles <a prolate spheroid>

spheroid: an object that is somewhat round but not perfectly round

If the two minor axes are not exactly equal then it's a bit muddled, but per the above Wikipedia article one could probably call it, e.g., a prolate tri-axial ellipsoid.

hmmn's answer is good in terms of emphasizing the extent to which the length of the major axis is greater than those of the minor axes, however.

To note, the above is in contrast to an ellipsoid where there are two long axes and one short axis, which is an oblate spheroid: