{ ‖ , n. pl. [ NL. anaerobia; an-not + aëro- + Gr.&unr_; life. ] (Bacteriol.) Anaërobic bacteria. They are called facultative anaërobes when able to live either in the presence or absence of free oxygen; obligate anaërobes, or obligatory anaërobes, when they thrive only in its absence. [ Webster 1913 Suppl. ]