acetabulum

acetabulum (noun; plural acetabula; Latin acetabulum, cup): 1. A cup-shaped socket or cavity.

2. (Annelida: Hirudinoidea) In leeches, the large posterior sucker.

3. (Arthropoda: Chelicerata) In Acari, the genital sucker.

4. (Arthropoda: Insecta) a. Any cavity into which an appendage is articulated; the coxal cavity. b. The conical cavity at the anterior of some larvae; in Diptera, the cavity in the sucking mouth. c. In dytiscid water beetles, stalked cuplets or sucker discs on the anterior tarsi, in some, also the second tarsi, thought to act as adhesive organs during copulation; a pallette.

5. (Echinodermata: Echinoidea) The cavity located on the proximal end of a spine.

6. (Mollusca: Cephalopoda) The sucker on the arm.

7. (Platyhelminthes: Cestoda) The sucker on the scolex.

8. (Platyhelminthes: Trematoda) The ventral sucker.