archaebacterium

noun

ar·​chae·​bac·​te·​ri·​um ˌär-kē-ˌbak-ˈtir-ē-əm 

: any of the microorganisms comprising the archaea : archaean

Note: The archaea were originally classified with the bacteria. They have since been placed in their own domain, and use of the term archaebacterium is now typically considered outmoded.

Word History

Etymology

New Latin

First Known Use

1977, in the meaning defined above