Geometry. a solid figure all plane sections of which are ellipses or circles. Typical equation: (x2/a2) + (y2/b2) + (z2/c2) = 1.


Origin of ellipsoid

From the French word ellipsoïde, dating back to 1715–25. See ellipse, -oid
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for ellipsoid

Historical Examples of ellipsoid

British Dictionary definitions for ellipsoid



  1. a geometric surface, symmetrical about the three coordinate axes, whose plane sections are ellipses or circles. Standard equation: x ²/ a ² + y ²/ b ² + z ²/ c ² = 1, where ± a, ± b, ± c are the intercepts on the x-, y-, and z- axes
  2. a solid having this shapethe earth is an ellipsoid
Derived Formsellipsoidal (ɪlɪpˈsɔɪdəl, ˌɛl-), adjective
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for ellipsoid

1721; see ellipse + -oid. From 1861 as an adjective (earlier adjective was ellipsoidal).

Online Etymology Dictionary, © 2010 Douglas Harper

ellipsoid in Science



A three-dimensional geometric figure resembling a flattened sphere. Any cross section of an ellipsoid is an ellipse or circle. An ellipsoid is generated by rotating an ellipse around one of its axes.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.