Definition of deltoid in US English:



  • 1Triangular.

    ‘a tree with large deltoid leaves’
    • ‘In some cases, the deltoid branch of the profunda brachii (16% of individuals) arises from the brachial or from the superior ulnar collateral.’
    • ‘Specimens are members of the Hyperoblastidae based on presence of four spiracles and anispiracle, deltoid crests (not faces), and two to four anideltoids.’
    • ‘The spiracles in orbitremitids pierce the adoral extremity of deltoid faces and are bounded laterally by ambulacral plates, which is the condition seen in the Chinese specimens.’
    • ‘Farther distally around the middle part of the shaft, is the deltoid tuberosity along the lateral border.’
    1. 1.1 Denoting a thick triangular muscle covering the shoulder joint and used for raising the arm away from the body.


  • 1A deltoid muscle.

    • ‘Evidence of a therapeutic effect can be seen by strengthening of the deltoid muscle on repeat muscle testing.’
    • ‘In many cases this is due to a genetic propensity of the deltoid and tricep muscles to be primarily involved in this pushing motion.’
    • ‘This is why each deltoid is made up of three heads, each of which has a separate function.’
    • ‘For example, if you're going to do heavy shoulder presses, you'll be using more than just your deltoids and triceps; the neck and trapezius muscles will be stressed as well.’
    • ‘Results of a comparison of the noninjured and the injured shoulder in the patient group showed that on both sides the deltoid muscle is active significantly earlier than the trapezius muscle.’
    • ‘Performed with or without assistance, pull-ups are a great way to strengthen the muscles of the upper body, particularly the latissimus dorsi, posterior deltoids and biceps.’
    • ‘Raise your arms out to your sides with your elbows slightly bent and wrists turned in, making sure not to use anything but your deltoids to raise the weight.’
    • ‘The most common substitution muscles are the biceps, triceps, deltoid and neck muscles.’
    • ‘Arms too far back reduces stress on the posterior deltoids and involves the trapezius and back muscles.’
    • ‘The intramuscular vaccine should be administered in the deltoid muscle and can be administered with other vaccines.’
    • ‘The trapezius may send a fascicle to the sternum and to the deltoid muscle.’
    • ‘This shoulder program focuses on the big, powerful deltoid as well as the smaller muscles that make up the rotator cuff.’
    • ‘Feel the three distinct heads of each deltoid contract and relax.’
    • ‘Strength training targeted 5 muscle groups (latissimus dorsi, pectorals, triceps / deltoid, hamstrings, and quadriceps).’
    • ‘The desired injection site is the outer aspect of the upper arm, midway between the shoulder and the elbow in the groove between the deltoid and triceps muscles.’
    • ‘He subsequently developed weakness in the deltoid, infraspinatus and supraspinatus muscles.’
    • ‘The cable crossover works the pectoralis major and minor, anterior deltoid, coracobrachialis and serratus anterior.’
    • ‘These vaccines are inactivated and should be administered intramuscularly into the deltoid muscle.’
    • ‘Tendinitis of the deltoid muscle tendon was ruled out as well.’
    • ‘If gravity were reduced or absent the deltoid's tension would raise the arm.’
    • ‘My deltoid muscles are too thick, it hurt to even try this new streamline.’
    • ‘During surgery, we observed partial or complete detachment of the trapezoid and deltoid muscles from the lateral clavicle in all patients.’
    • ‘What's more, it builds what powerlifters call ‘accessories’: biceps, triceps, deltoids, abs and other vanity muscles.’
    • ‘The skin over the deltoid muscle or posterior arm is the most common vaccination site.’
    • ‘After getting eight to 12 reps, lie on your left side to work your right medial deltoid.’
    1. 1.1 Each of the three parts of a deltoid muscle, attached at the front, side, and rear of the shoulder.
      ‘the anterior deltoid’
      • ‘One key to shoulder training is to think of your front, side and rear deltoids as distinct (but small) muscles.’
      • ‘The front deltoids and the triceps are recruited as secondary muscles.’
      • ‘This works the trapezius and front deltoids together.’
      • ‘The rear deltoid, teres minor and infraspinatus are responsible.’
      • ‘The heavier you can go with your bench-press sets, the better for your pectorals, anterior deltoids and triceps, provided their work is not being stolen by cheating.’
      • ‘Hold your shoulders low, so that only your anterior deltoid, not your trapezius, performs the lift.’


Mid 18th century: from French deltoïde, or via modern Latin from Greek deltoeidēs.