Wiktionary
acetabular labrum
n. (context anatomy English) A ring of cartilage that surrounds the socket of the hip joint.
Wikipedia
Acetabular labrum
The acetabular labrum (glenoidal labrum of the hip joint or cotyloid ligament in older texts) is a ring of cartilage that surrounds the acetabulum of the hip. The anterior portion is most vulnerable when the labrum tears.
It provides an articulating surface for the acetabulum, allowing the head of the femur to articulate with the pelvis.