coccidium

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of various parasitic protozoans belonging to the order Coccidia and responsible for a disease of the alimentary canal in livestock, fowl, and humans.

Century Dictionary and Cyclopedia

1. n. Pl. coccidia (-ä). In botany, a name given by Harvey to a form of conceptacle found in certain red algæ, borne on lateral branches, or sessile on the surface of the frond, and usually not opening by a pore. The spores within are attached to a central placenta.
2. n. A genus of gregarines.
3. n. [lowercase] One of the coccidiidea.

GNU Webster's 1913

1. n. (Microbiol.) any sporozoan of the order Coccidia, parasitic on the digestive epithelium of vertebrates and higher invertebrates. It is the causative agent of coccidiosis, which can be a problem in poultry rearing.

WordNet 3.0

1. n. parasitic on the digestive epithelium of vertebrates and higher invertebrates