Question: the joint between a coxal bone of the pelvis and the sacrum?
Evidence: The ilium is where the sacrum attaches to each coxal bone to complete the pelvic bowl. This attachment point is alternatively called the sacroiliac joint, the sacroiliac articulation, or the iliac tuberosity, and is a rough surface. In anatomical position, the rough sacroiliac joint is always facing anterior.
Answer: sacroiliac joint