Iliolumbar is a term used in anatomy to describe the area around the lower back where the iliac crest and lumbar vertebrae meet. Some synonyms for Iliolumbar include lumbopelvic region, lumbosacral region, lumbosacral junction, and lumboiliac region. Other related terms include sacroiliac joint, which is where the sacrum and ilium meet, and lumbar spine, which refers to the section of the spine that contains the five vertebrae between the ribcage and pelvis. These terms are commonly used in medical literature and discussions regarding back pain or injury in this area.