acetabulum > define

noun

• The cup-shaped hollow in the hipbone into which the head of the femur fits to form a ball-and-socket joint.
  • synonyms: cotyloid cavity

• (n.) A vinegar cup; socket of the hip bone; a measure of about one eighth of a pint, etc.
• (n.) The bony cup which receives the head of the thigh bone.
• (n.) The cavity in which the leg of an insect is inserted at its articulation with the body.
• (n.) A sucker of the sepia or cuttlefish and related animals.
• (n.) The large posterior sucker of the leeches.
• (n.) One of the lobes of the placenta in ruminating animals.