• synonyms


  1. Geometry. a solid figure all plane sections of which are ellipses or circles. Typical equation: (x2/a2) + (y2/b2) + (z2/c2) = 1.
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  1. ellipsoidal.
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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. 2018

Examples from the Web for ellipsoid

Historical Examples

  • The fruit is a small, ellipsoid drupe, which is bluish-black when ripe.

    Fruits of the Hawaiian Islands

    Gerrit Parmile Wilder

  • Of the two eggs, one is of an ovoid form, having much the shape of a hen's egg; and the other is an ellipsoid.

  • Its form is that of an ellipsoid, with a major axis 26 millimetres in length, while the minor axis measures 11 millimetres.

    More Hunting Wasps

    J. Henri Fabre

  • The form of the latter is at first globular, then ellipsoid, and more or less curved.

    Fungi: Their Nature and Uses

    Mordecai Cubitt Cooke

  • Sporangia globose or ovoid to ellipsoid or oblong, erect or sometimes inclined or even nodding.

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
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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).

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Online Etymology Dictionary, © 2010 Douglas Harper

ellipsoid in Science


  1. 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.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.