Deltoid: The muscle, roughly triangular in shape, that stretches from the collarbone (clavicle) over the shoulder to the upper bone of the arm (humerus). It contracts to move the arm up from the side.
Deltoid: The muscle, roughly triangular in shape, that stretches from the collarbone (clavicle) over the shoulder to the upper bone of the arm (humerus). It contracts to move the arm up from the side.
