Wiktionary
spondylolysis
n. (context pathology English) A defect of the pars interarticularis.
Wikipedia
Spondylolysis
Spondylolysis (spon-dee-low-lye-sis) is defined as a defect or stress fracture in the pars interarticularis of the vertebral arch. The vast majority of cases occur in the lower lumbar vertebrae (L5), but spondylolysis may also occur in the cervical vertebrae.