# ellipsoid

> English word · Noun · IPA /ɪˈlɪp.sɔɪd/ · frequency rank #60,056

## Definitions
1. A surface, all of whose cross sections are elliptic or circular (including the sphere), that generalises the ellipse and in Cartesian coordinates (x, y, z) is a quadric with equation x²/a² + y²/b² + z²/c² = 1.
2. Such a surface used as a model of the shape of the earth.

## Etymology
From ellipse + -oid.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/ellipsoid