del·​toid | \ ˈdel-ˌtȯid How to pronounce deltoid (audio) \

Definition of deltoid

 (Entry 1 of 2)

: a large triangular muscle that covers the shoulder joint and serves to raise the arm laterally



Definition of deltoid (Entry 2 of 2)

1 : having a triangular shape a deltoid leaf — see leaf illustration
2 : relating to, associated with, or supplying the deltoid

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Did You Know?

The fourth letter of the Greek alphabet is delta, and a capital delta is triangle-shaped. In English, delta commonly means the sand deposits that form a huge triangle at the mouth of certain large rivers. Deltoid as an adjective means "having a triangular shape", and botanists often use the word to describe the shape of certain leaves. The triangular, swept-back wings seen on jet fighter aircraft are called delta wings. Your deltoid muscles—not far from your rhomboids—form a cap on your shoulders, and some gym trainers even treat shoulder and deltoid as synonyms. Can you guess the general shape of deltoids when seen from the side?

Examples of deltoid in a Sentence

Recent Examples on the Web: Noun This combination of exercises will hit your triceps, biceps, pectoralis muscles, and muscles in the shoulders and upper back, including the rhomboids, deltoids, rhomboids, traps, and lats. Amy Marturana, SELF, "An Easy and Effective Dumbbell Arm, Back, and Chest Workout," 9 Feb. 2019 Van Der Beek’s deltoids and obliques are much more defined after the dance training, possibly from all the twists and lifts. Kelsey Hurwitz, Woman's Day, "'DWTS' Star James Van Der Beek Shows Off Transformed Body On Instagram," 2 Dec. 2019 Turay had dislocated his ankle, tore the deltoid ligament in his right ankle and suffered a fracture. Joel A. Erickson, Indianapolis Star, "Colts DE Kemoko Turay to 'constantly work my butt off' after gruesome leg injury," 17 Oct. 2019 The worry is for injury to the syndesmotic ligament that holds the fibula and tibia together, as well as the deltoid ligament. San Diego Union-Tribune, "Saquon Barkley will miss time with ankle injury," 22 Sep. 2019 Targets the core, pectorals, deltoids, and triceps. SELF, "A 15-Minute No-Equipment Core Workout You Can Do at Home," 18 Jan. 2019 The rolling out movement primarily works your lats and deltoids, whereas the second half of the movement—the rolling in portion—really targets your core, specifically your rectus abdominis, says Brewer. Jenny Mccoy, SELF, "Why the Ab Wheel Is Such a Challenging and Effective Workout Tool," 6 Dec. 2018 Deadlifts already work the posterior chain, or the muscles at the rear of the body like the hamstrings, gluteus maximus, trapezius, posterior deltoids, and erector spinae. Leah Prinzivalli, SELF, "Why the Deficit Deadlift Is a Great Modification for Beginners," 5 Dec. 2018 Shots given in muscles — like the deltoid in the upper arm where flu shots are usually given — tend to be more painful than ones that aren't injected into the muscle, Stewart said. Erica Sweeney, Teen Vogue, "Why Do Some Vaccines Hurt More Than Others?," 24 Oct. 2018 Recent Examples on the Web: Adjective Her pectoralis major and deltoid muscles, for example, had been used to draw a bow across her chest. Fox News, "Tomb of battle-scarred ancient female warrior reveals its secrets," 30 Nov. 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'deltoid.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of deltoid


circa 1681, in the meaning defined above


circa 1753, in the meaning defined at sense 1

History and Etymology for deltoid


New Latin deltoides, from Greek deltoeidēs shaped like a delta, from delta

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Time Traveler for deltoid

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The first known use of deltoid was circa 1681

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Cite this Entry

“Deltoid.” Dictionary, Merriam-Webster, Accessed 30 Oct. 2020.

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More Definitions for deltoid


How to pronounce deltoid (audio)

English Language Learners Definition of deltoid

: a large muscle of the shoulder


del·​toid | \ ˈdel-ˌtȯid How to pronounce deltoid (audio) \

Medical Definition of deltoid

 (Entry 1 of 2)

: a large triangular muscle that covers the shoulder joint, serves to raise the arm laterally, arises from the upper anterior part of the outer third of the clavicle and from the acromion and spine of the scapula, and is inserted into the outer side of the middle of the shaft of the humerus

called also deltoid muscle

— see deltoid tuberosity



Medical Definition of deltoid (Entry 2 of 2)

: relating to, associated with, or supplying the deltoid the deltoid branch of the thoracoacromial artery

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