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[del-toid] /ˈdɛl tɔɪd/
Anatomy. a large, triangular muscle covering the joint of the shoulder, the action of which raises the arm away from the side of the body.
Anatomy. pertaining to or involving the deltoid.
Also, deltoidal. in the shape of a Greek capital delta (Δ); triangular.
Origin of deltoid
1675-85; < Greek deltoeidḗs delta-shaped, equivalent to délt(a) delta + -oeidēs -oid
Related forms
subdeltoid, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for deltoid
Historical Examples
  • deltoid: elongate triangular: resembling a Greek D with apex extended.

  • The part of this muscle which arises from the humerus is covered by the deltoid.

  • It is necessary to add that the deltoid is inserted into the humerus, above the insertion of the mastoido-humeral.

  • The arm is divided into three sections: the deltoid, brachial and carpal.

  • deltoid ridge moderately prominent, irregular, rugose, and extending to about the middle of the shaft.

  • A single muscle, the deltoid, in this case does most of the work.

    A Practical Physiology Albert F. Blaisdell
  • I imagined that I could detect, at the height of my deltoid muscle, the exact spot where the sleeve of her under-garment ended.

    The Confession of a Fool August Strindberg
  • Above this groove, and on the external surface, there exists a rough surface which is the impression of the deltoid.

  • Tom Sayers says Skeffy's deltoid—that's the muscle up here—is finer than any in the ring, and he's such an active devil.

    Tony Butler Charles James Lever
  • But the others scornfully suggested that the deltoid was a muscle; they knew, because they had dissected one that very morning.

    Out of the Hurly-Burly Charles Heber Clark
British Dictionary definitions for deltoid


the thick muscle forming the rounded contour of the outer edge of the shoulder and acting to raise the arm
shaped like a Greek capital delta, Δ; triangular
Word Origin
C18: from Greek deltoeidēs triangular, from delta
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
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Word Origin and History for deltoid

1741, in deltoid muscle, so called for its shape, from Greek deltoeides "triangular," literally "shaped like the letter delta;" see delta + -oid.

Online Etymology Dictionary, © 2010 Douglas Harper
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deltoid in Medicine

deltoid del·toid (děl'toid')

  1. Of or relating to the deltoid muscle.

  2. Triangular in shape or outline.

The deltoid muscle.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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