n, pl  -les   :  any of three muscles of the cervical and thoracic parts of the spinal column that arise from transverse processes of the vertebrae and pass to spinous processes higher up and that help to form a layer underneath the sacrospinalis muscle:  a  :  SEMISPINALIS THORACIS  b  :  SEMISPINALIS CERVICIS  c  :  SEMISPINALIS CAPITIS .
 
 
 
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