Acetabulum \Ac`e*tab"u*lum\, n. [L., a little saucer for vinegar, fr. acetum vinegar, fr. acere to be sour.]

1. (Rom. Antiq.) A vinegar cup; socket of the hip bone; a measure of about one eighth of a pint, etc.

2. (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.

Source: Webster's Revised Unabridged Dictionary (1913)