latissimus dorsi

noun, plural la·tis·si·mi dor·si [luh-tis-uh-mahy dawr-sahy] /ləˈtɪs əˌmaɪ ˈdɔr saɪ/. Anatomy.

1. a broad, flat muscle on each side of the midback, the action of which draws the arm backward and downward and rotates the front of the arm toward the body.

n.

1. A muscle with origin from the spinous processes of the lower thoracic and lumbar vertebrae, the median ridge of the sacrum, and the outer lip of the iliac crest, with insertion into the humerus, with nerve supply from the thoracodorsal nerve, and whose action adducts the arm, rotates it medially, and extends it.