An ellipsoidal dome is a dome (also see geodesic dome), which has a bottom cross-section which is a circle, but has a cupola whose curve is an ellipse.[1]
There are two types of ellipsoidal domes: prolate ellipsoidal domes and oblate ellipsoidal domes. A prolate ellipsoidal dome is derived by rotating an ellipse around the long axis of the ellipse; an oblate ellipsoidal dome is derived by rotating an ellipse around the short axis of the ellipse.[2]
Of small note, in reflecting telescopes the mirror is usually elliptical, so has the form of a "hollow" ellipsoidal dome.
The Jameh Mosque of Yazd has an ellipsoidal dome.[3]