rickettsia(n = noun.animal) - any of a group of very small rod-shaped bacteria that live in biting arthropods (as ticks and mites) and cause disease in vertebrate hosts; they cause typhus and other febrile diseases in human beings;
is a kind of eubacteria, eubacterium, true bacteria
is a member of family rickettsiaceae, rickettsiaceae
Derived form adjective rickettsial₁

rickettsia, n. a parasitic micro-organism of the genus Rickettsia causing typhus and other febrile diseases.

Derivative:
rickettsial adj.

Etymology:
mod.L f. H. T. Ricketts, Amer. pathologist d. 1910

genus rickettsia