[ ri-ket-see-uh ]
/ rɪˈkɛt si ə /

noun, plural rick·ett·si·ae [ri-ket-see-ee] /rɪˈkɛt siˌi/, rick·ett·si·as [ri-ket-see-uh z] /rɪˈkɛt si əz/.

any member of the genus Rickettsia, comprising rod-shaped to coccoid microorganisms that resemble bacteria but can be as small as a large virus and reproduce only inside a living cell, parasitic in fleas, ticks, lice, and mites and transmitted by bite to vertebrate hosts, including humans, causing such severe diseases as typhus and Rocky Mountain spotted fever.
any rickettsia or rickettsialike microorganism of the orders Rickettsiales and Chlamydiales.

Origin of rickettsia

1915–20; < New Latin, after Howard T. Ricketts (1871–1910), U.S. pathologist; see -ia


rick·ett·si·al, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for rickettsia

/ (rɪˈkɛtsɪə) /

noun plural -siae (-sɪˌiː) or -sias

any of a group of parasitic bacteria that live in the tissues of ticks, mites, and other arthropods, and cause disease when transmitted to man and other animals

Derived forms of rickettsia

rickettsial, adjective

Word Origin for rickettsia

C20: named after Howard T. Ricketts (1871–1910), US pathologist
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medicine definitions for rickettsia

[ rĭ-kĕtsē-ə ]


A genus of gram-negative bacteria that are carried as parasites by many ticks, fleas, and lice and cause diseases such as typhus, scrub typhus, and Rocky Mountain spotted fever.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.