[ 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.

Nearby words

  1. delta wing,
  2. delta-aminolevulinic acid,
  3. deltaic,
  4. deltiological,
  5. deltiology,
  6. deltoid ligament,
  7. deltoid muscle,
  8. deltoidal,
  9. delts,
  10. delubrum

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

British Dictionary definitions for deltoid


/ (ˈdɛltɔɪd) /


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

Medicine definitions for deltoid


[ dĕltoid′ ]


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.