Any of a number of short transversospinal muscles chiefly developed in cervical, lumbar, and thoracic regions, arising from the transverse process of one vertebra and inserted into the root of the spinous process of the next two or three vertebrae above, with nerve supply from the dorsal branches of the spinal nerve, and whose actions rotate the vertebral column. [ http://medical-dictionary.thefreedictionary.com/rotator+muscle ]