cloaca

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A sewer or latrine.
2. n. Zoology The common cavity into which the intestinal, genital, and urinary tracts open in vertebrates such as fish, reptiles, birds, and some primitive mammals.
3. n. Zoology The posterior part of the intestinal tract in various invertebrates.

Century Dictionary and Cyclopedia

1. n. An underground conduit for drainage; a common sewer: as, the cloaca maxima at Rome.
2. n. A sink; a privy.
3. n. [NL.] In zoology: In vertebrates, the enlarged termination of the rectum or lower bowel, forming a cavity originally in common with that of the allantois (in those animals which have an allantois) and permanently in common with the termination of the urogenital organs; the common chamber into which the intestine, ureters, sperm-ducts, and oviducts open, in sundry fishes, in reptiles and birds, and in the ornithodelphous mammals. This cavity is the common sewer of the body, receiving the refuse of digestion, the product of conception, the spermatic secretion, and the renal excretion, all to be discharged through the anal orifice. It is more or less incompletely divided into the cloaca proper, or the enlarged end of the rectum, and the urogenital sinus, a compartment in which terminate the ureters, sperm-ducts, and oviducts, and which contains the penis or clitoris when those organs are developed. There is no cloaca in adult mammals, with the exception of the monotremes, the separation of the urogenital sinus from the digestive tube being complete in all the others.
4. n. In invertebrates, the homologous or analogous and corresponding structure effecting sewerage of the body: as in sponges, the common cavity in which the interstitial canal-systems open; in holothurians, the respiratory tree (which see, under respiratory).
5. n. In entomology: A cavity found in many insects at the end of the abdomen, between the last dorsal and ventral segments, and receiving the extremity of the rectum. Also called the rectogenital chamber. The cæcum, or dilatation of the posterior end of the intestine.
6. n. In ascidians, the common central cavity into which open the atrial chambers of all the ascidiozooids of an ascidiarium.
7. n. [NL.] In pathology: In cases of necrosis, the opening in the sound bone which leads to the inclosed dead bone.
8. n. The union of rectum, bladder, and organs of generation in a common outlet: a malformation resulting from arrest of development.

Wiktionary

1. n. A sewer.
2. n. A privy.
3. n. anatomy The common duct in fish, reptiles, birds and some primitive mammals that serves as the anus as well as the genital opening.

GNU Webster's 1913

1. n. A sewer.
2. n. A privy.
3. n. (Anat.) The common chamber into which the intestinal, urinary, and generative canals discharge in birds, reptiles, amphibians, and many fishes.

WordNet 3.0

1. n. (zoology) the cavity (in birds, reptiles, amphibians, most fish, and monotremes but not mammals) at the end of the digestive tract into which the intestinal, genital, and urinary tracts open
2. n. a waste pipe that carries away sewage or surface water