Acetabular: Pertaining to the acetabulum, the cup-shaped socket of the hip joint which is a key feature of the pelvis. The head (upper end) of the femur (the thighbone) fits into the acetabulum and articulates with it, forming a ball-and-socket joint.

The acetabulum is not just cup-shaped. The word "acetabulum" in Latin means cup, a vinegar cup.