Definition of deltoid in 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.’
    • ‘Farther distally around the middle part of the shaft, is the deltoid tuberosity along the lateral border.’
    • ‘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.’
    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.

    • ‘This shoulder program focuses on the big, powerful deltoid as well as the smaller muscles that make up the rotator cuff.’
    • ‘After getting eight to 12 reps, lie on your left side to work your right medial deltoid.’
    • ‘The cable crossover works the pectoralis major and minor, anterior deltoid, coracobrachialis and serratus anterior.’
    • ‘Feel the three distinct heads of each deltoid contract and relax.’
    • ‘This is why each deltoid is made up of three heads, each of which has a separate function.’
    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’
      • ‘The rear deltoid, teres minor and infraspinatus are responsible.’
      • ‘The front deltoids and the triceps are recruited as secondary muscles.’
      • ‘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.’
      • ‘One key to shoulder training is to think of your front, side and rear deltoids as distinct (but small) muscles.’
      • ‘Hold your shoulders low, so that only your anterior deltoid, not your trapezius, performs the lift.’
      • ‘This works the trapezius and front deltoids together.’


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