| rickettsiales | (n) pleomorphic Gram-negative microorganisms, Syn. order Rickettsiales |
| rickettsia | (n) 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 |
| rickettsiaceae | (n) microorganism resembling bacteria inhabiting arthropod tissues but capable of causing disease in vertebrates, Syn. family Rickettsiaceae |
| rickettsial | (adj) relating to or caused by rickettsias |
| rickettsial disease | (n) infectious disease caused by ticks or mites or body lice infected with rickettsial bacteria, Syn. rickettsiosis |
| rickettsialpox | (n) mild infectious rickettsial disease caused by a bacterium of the genus Rickettsia transmitted to humans by the bite a mite that lives on rodents; characterized by chills and fever and headache and skin lesions that resemble chickenpox |