(formerly) a group of microorganisms now regarded as members of the Archaea
archaean
Word origin
from archaeo- + bacteria
archaebacteria in American English
(ˌɑrkibækˈtɪriə)
plural nounWord forms: singularˌarchaebacˈterium (ˌɑrkibækˈtɪrəm) or ˌarchaebacˈteria
any of a large group of primitive bacteria having unusual cell walls, membrane lipids, ribosomes, and RNA sequences, and having the ability to produce methane and to live in anaerobic, extremely hot, salty, or acidic conditions; archaea