Microdiscectomy: a type of surgery also referred to as microdecompression or microdiskectomy. Microdiscectomy is a minimally invasive surgical procedure using a microscope to view and remove portions of a herniated disc in the spinal cord. This is usually done for a herniated lumbar (low back) disc that is causing symptoms due to irritation of or pressure on a nerve root. The part of the disc that is irritating the nerve root is removed. Microdiscectomy is performed through a small incision in the midline of the low back.