acetabulum

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Anatomy The cup-shaped cavity at the base of the hipbone into which the ball-shaped head of the femur fits.
2. n. Zoology The cavity in the body of an insect into which the leg fits.
3. n. Zoology A cup-shaped structure, such as the sucker of a tapeworm or leech.

Century Dictionary and Cyclopedia

1. n. In Roman antiquity: A vinegar-cup; a small wide-mouthed vessel of earthenware or metal, sometimes placed on the larger food-dishes, in which vinegar or other condiment was served. A dry or liquid measure, .0677 of a liter. Daremberg et Saglio. A similar cup or vessel used by jugglers in their feats.
2. n. In anatomy: The cavity of the os innominatum, or hip-bone, which receives the head of the femur; the cotyle, or cotyloid cavity, formed at the junction of the ilium, ischium, and pubis. See cuts under sacrarium, quarter, innominate. A cotyledon or lobe of the placenta of ruminating animals. In insects, the socket of the trunk in which the leg is inserted. A cup-like sucker, such as those with which the arms of the cuttlefish and other dibranchiate cephalopodous mollusks are provided. See cut under Sepia. A sessile or pedunculate sucker-like organ on the ventral surface of certain entozoa.
3. n. In botany: The cup- or saucer-like fructification of many lichens. The receptacle of certain fungi.
4. n. In music, an ancient instrument, made either of earthenware or of metal, used like a kettledrum or struck against another acetabulum after the manner of cymbals.
5. n. [capitalized] A genus of calcareous green algæ, Chlorophyceæ, found in tropical or subtropical waters: characterized by anerectaxis surmounted by a solid cap which consists of numerous radiating chambers. Also Acetabularia.

Wiktionary

1. n. Roman Antiquities a vinegar cup;
2. n. Roman Antiquities the socket of the hipbone;
3. n. Roman Antiquities a measure of about one eighth of a pint
4. n. anatomy The bony cup which receives the head of the thigh bone.
5. n. anatomy The cavity in which the leg of an insect is inserted at its articulation with the body.
6. n. anatomy A sucker of the sepia or cuttlefish and related animals.
7. n. anatomy The large posterior sucker of the leeches.
8. n. anatomy One of the lobes of the placenta in ruminating animals.

GNU Webster's 1913

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

WordNet 3.0

1. n. the cup-shaped hollow in the hipbone into which the head of the femur fits to form a ball-and-socket joint