multifidus muscle mul·tif·i·dus muscle (mŭl-tĭf'ĭ-dəs)
n.
A muscle with origin from the sacrum, the sacroiliac ligament, the lumbar vertebrae, the thoracic vertebrae, and the last four cervical vertebrae, with insertion into the spinous processes of all the vertebrae up to and including the axis; with nerve supply from the dorsal branches of the spinal nerve; and whose action rotates the vertebral column.