n, pl  la*tis*si*mi dorsi   :  a broad flat superficial muscle of the lower part of the back that originates mostly in a broad aponeurosis attached to the spinous processes of the vertebrae of the lower back, the supraspinal ligament, and the crest of the ilium, that is inserted into the bicipital groove of the humerus, and that extends, adducts, and rotates the arm medially and draws the shoulder downward and backward .
 
 
 
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