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 formssub·del·toid, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for deltoid

Historical Examples of deltoid

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 for deltoid

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

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

deltoid in Medicine




Of or relating to the deltoid muscle.
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.