a person of the ectomorphic type.

1935–40; ecto- + -morph Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
ectomorph (ˈɛktəʊˌmɔːf)
endomorph Compare mesomorph a person with a thin body build: said to be correlated with cerebrotonia

Collins English Dictionary - Complete & Unabridged 10th Edition
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Word Origin & History

1940, coined by Sheldon from ecto- + Gk. morphe (see morphine). Related: Ectomorphic.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

ectomorph ec·to·morph (ěk'tə-môrf')
An individual having a lean, slightly muscular body build in which tissues derived from the embryonic ectoderm predominate.

ec'to·mor'phic adj.
ec'to·mor'phy n.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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Encyclopedia Britannica


a human physical type (somatotype) tending toward linearity, as determined by the physique classification system developed by the American psychologist W.H. Sheldon. Although classification by the Sheldon system is not absolute, a person is classed as an ectomorph if ectomorphy predominates over endomorphy and mesomorphy in his body build. The extreme ectomorph has a thin face with high forehead and receding chin; narrow chest and abdomen; a narrow heart; rather long, thin arms and legs; little body fat and little muscle; but a large skin surface and a large nervous system. If well fed he does not gain weight easily, and if he becomes fat he is still considered an ectomorph, only overweight. Compare endomorph; mesomorph.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
The ectomorph was likely to be intelligent and sensitive but tended toward nervousness and secretiveness.
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