What does "acetabulum" mean?

Acetabulum: (Anat.) (a) The bony cup which receives the head of the thigh bone. (b) The cavity in which the leg of an insect is inserted at its articulation with the body. (c) A sucker of the sepia or cuttlefish and related animals. (d) The large posterior sucker of the leeches. (e) One of the lobes of the placenta in ruminating animals.