ACETAB'ULUM, noun [Latin from acetum, vinegar. See Acid.] Among the Romans a vinegar cruse or like vessel, and a measure of about one eighth of a pint.

1. In anatomy, the cavity of a bone for receiving the protuberant end of another bone, and therefore forming the articulation called enarthrosis. It is used especially for the cavity of the os innominatum, which receives the head of the thigh bone.

2. In botany, the trivial name of a species of peziza, the cup peziza; so called from its resemblance to a cup.

3. A glandular substance found in the placenta of some animals.

4. It is sometimes used in the sense of Cotyledon.

5. A species of lichen.