deltoid

American  

[del-toid] / ˈdɛl tɔɪd /

noun

1. 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.

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adjective

1. Anatomy. pertaining to or involving the deltoid.

2. Also in the shape of a Greek capital delta (Δ); triangular.

deltoid British  

/ ˈdɛltɔɪd /

noun

1. the thick muscle forming the rounded contour of the outer edge of the shoulder and acting to raise the arm

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adjective

1. shaped like a Greek capital delta, Δ; triangular

Other Word Forms

• subdeltoid
  adjective

Etymology

Origin of deltoid

1675–85; < Greek deltoeidḗs delta-shaped, equivalent to délt ( a ) delta + -oeidēs -oid

Explanation

Your deltoid is your shoulder muscle — it makes up the rounded part of your shoulder and allows you to twist, raise, and extend your arms. When deltoid is used as an adjective, it means "triangular," so you could describe your A-frame house or pup tent as deltoid. The deltoid muscle got its name because of its triangular shape and its three distinct sections of muscle fibers. Weight lifters and body builders sometimes call these muscles "delts" for short. Deltoid comes from the Greek deltoeides, "triangular," or "shaped like the Greek letter delta."

Example Sentences

British actor Aubrey Morris, best known for playing probation officer Mr Deltoid in Stanley Kubrick's 1971 film A Clockwork Orange, has died aged 89.

From BBC • Jul. 17, 2015

Deltoid, of a triangular shape, like the Greek capital Δ. Demersed, growing below the surface of water.

From The Elements of Botany For Beginners and For Schools by Gray, Asa

Deltoid, having the shape of the Greek letter delta; broadly triangular.

From The Wild Flowers of California: Their Names, Haunts, and Habits by Parsons, Mary Elizabeth

Deltoid: elongate triangular: resembling a Greek D with apex extended.

From Explanation of Terms Used in Entomology by Smith, John. B.

Related Words

• trilateral