AskDefine | Define oblate

Dictionary Definition

oblate adj : having the equatorial diameter greater than the polar diameter; being flattened at the poles [syn: pumpkin-shaped] [ant: prolate] n : a lay person dedicated to religious work or the religious life

User Contributed Dictionary



  • a UK /ˈɒbleɪt/
  • a US /ˈɑbleɪt/

Etymology 1

From French oblat and its source, post-classical Latin oblatus ‘person dedicated to religious life’, a noun use of the past participle of offerre ‘to offer’.


  1. italbrac Roman Catholic Church A person dedicated to a life of religion or monasticism, especially a member of an order without religious vows or a lay member of a religious community.
  2. A child given up by its parents into the keeping or dedication of a religious order or house.
    • 2007: The Venerable Bede started as an oblate at St Paul's, Jarrow, but by the time of his death in 735 was surely the most learned man in Europe. — Tom Shippey, ‘I Lerne Song’, London Review of Books 29:4, p. 19
Related terms

Etymology 2

From oblatus, from ob + lātus, (modelled after prolatus).


  1. Flattened or depressed at the poles.
    • 1922: Why should I not speak to him or to any human being who walks upright upon this oblate orange? — James Joyce, Ulysses
    • 1997: ‘ ’Tis prolate, still,’ with a long dejected Geordie O. ‘Isn’t it…?’ ‘I’m an Astronomer,– trust me, ’tis gone well to oblate.’ — Thomas Pynchon, Mason & Dixon
Related terms

Extensive Definition

An oblate spheroid is a rotationally symmetric ellipsoid having a polar axis shorter than the diameter of the equatorial circle whose plane bisects it. An M&M's candy (plain) (US) or Smartie (Canada, UK and Europe) is an approximate example of an oblate spheroid.
It can be formed by rotating an ellipse about its minor axis, forming an equator with the end points of the major axis. As with all ellipsoids, it can also be described by the lengths of three mutually perpendicular principal axes, which are in this case two arbitrary equatorial semi-major axes and one semi-minor axis.
The opposite of oblate is prolate.
For a discussion of the physics that determines the shape of a spinning celestial body, see Equatorial bulge
The aspect ratio, b:a, is the ratio of the polar to equatorial lengths , while the flattening (also called oblateness), f, is the ratio of the equatorial-polar length difference to the equatorial length:
f=\frac=1 - \frac.\,\!
These are just two of several different parameters used to define an ellipse and its solid body counterparts, all of which are ultimately trigonometric functions of the ellipse's modular angle, or angular eccentricity.
The oblate spheroid is interesting because it is the approximate shape of many planets and celestial bodies, including most notably Saturn and Altair, but also to a lesser extent the Earth (with a = 6378.137 km and b ≈ 6356.752 km, providing an aspect ratio of 0.99664717 and inverse flattening of 298.2572 [1]). It is therefore the geometric figure most used for defining reference ellipsoids, upon which cartographic and geodetic systems are based.

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oblate in Bulgarian: Сплеснатост
oblate in Catalan: Esferoide oblat
oblate in Danish: Fladtrykthed
oblate in French: Aplatissement
oblate in Norwegian Nynorsk: Flattryktheit
oblate in Slovenian: Sploščen sferoid
oblate in Vietnamese: Hình cầu dẹt
oblate in Chinese: 扁率
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